Configurable reference signals

ABSTRACT

It is recognized herein that current LTE reference signals may be inadequate for future cellular (e.g., New Radio) systems. Configurable reference signals are described herein. The configurable reference signals can support mixed numerologies and different reference signal (RS) functions. Further, reference signals can be configured so as to support beam sweeping and beamforming training.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a continuation of U.S. patent application Ser. No.17/019,489 filed Sep. 14, 2020, which is a continuation of U.S. patentapplication Ser. No. 16/093,287 filed Oct. 12, 2018, which is a NationalStage Application filed under 35 U.S.C. § 371 of InternationalApplication No. PCT/US2017/028633 filed Apr. 20, 2017, which claims thebenefit of priority to U.S. Provisional Patent Application No.62/325,394, filed Apr. 20, 2016, U.S. Provisional Patent Application No.62/338,350, filed May 18, 2016, U.S. Provisional Patent Application No.62/373,176, filed Aug. 10, 2016 and U.S. Provisional Patent ApplicationNo. 62/416,902 filed Nov. 3, 2016 the disclosures of which areincorporated by reference in their entireties.

BACKGROUND

The 3rd Generation Partnership Project (3GPP) develops technicalstandards for cellular telecommunications network technologies,including radio access, the core transport network, and servicecapabilities—including work on codecs, security, and quality of service.Recent radio access technology (RAT) standards include WCDMA (commonlyreferred as 3G), LTE (commonly referred as 4G), and LTE-Advancedstandards. 3GPP has begun working on the standardization of nextgeneration cellular technology, called New Radio (NR), which is alsoreferred to as “5G”. 3GPP NR standards development is expected toinclude the definition of next generation radio access technology (newRAT), which is expected to include the provision of new flexible radioaccess below 6 GHz, and the provision of new ultra-mobile broadbandradio access above 6 GHz. The flexible radio access is expected toconsist of a new, non-backwards compatible radio access in new spectrumbelow 6 GHz, and it is expected to include different operating modesthat can be multiplexed together in the same spectrum to address a broadset of 3GPP NR use cases with diverging requirements. The ultra-mobilebroadband is expected to include cmWave and mmWave spectrum that willprovide the opportunity for ultra-mobile broadband access for, e.g.,indoor applications and hotspots. In particular, the ultra-mobilebroadband is expected to share a common design framework with theflexible radio access below 6 Ghz, with cmWave and mmWave specificdesign optimizations.

In Long term Evolution (LTE), downlink (DL) reference signals (RSs) arepredefined signals occupying specific resource elements (REs) within thedownlink time-frequency RE grid. LTE defines several types of DL RSsthat are transmitted in different ways for different purposes. Forexample, a cell-specific reference signal (CRS) can be transmitted inevery DL subframe and in every Resource Block (RB) in the frequencydomain (e.g., see FIG. 1). A CRS may be used: (1) by terminals forchannel estimation for coherent demodulation of DL physical channels;(2) by terminals to acquire Channel State Information (CSI) configuredin transmission modes 1 to 8 as shown Table 1 below (e.g., supporting upto 4 antenna ports); or (3) by terminals as the basis for cell-selectionand handover decisions.

TABLE 1 Transmission Modes in LTE Trans- LTE mission Rel ModeDescription 8 1 Single-antenna transmission 8 2 Transmit diversity 8 3Open-loop codebook-based precoding in the case of more than one layer,transmit diversity in the case of rank-one transmission 8 4 Closed-loopcodebook-based precoding 8 5 Multi-user-MIMO version of transmissionmode 4 8 6 Special case of closed loop codebook-based precoding limitedto single-layer transmission 8 7 Non-codebook-based precoding supportingsingle-layer PDSCH transmission 9 8 Non-codebook-based precodingsupporting up to two layers 10 9 Non-codebook-based precoding supporting8 layers 11 10 Extension of transmission mode 9 for enhanced support ofdifferent means of DL multi-point coordination and transmission, alsoreferred to as CoMP

Demodulation Reference Signals (DM-RSs) are another example of a DL RS.A DM-RS can be referred to as User Equipment (UE)-specific referencesignals that are intended to be used by terminals for channel estimationfor coherent demodulation of Physical Downlink Shared CHannel (PDSCH) incase of transmission modes 7 to 10 (as shown in Table 1) and EnhancedPhysical Downlink Control CHannel (EPDCCH). DM-RSs may be used forchannel estimation by a specific UE, and then transmitted within the RBsspecifically assigned for PDSCH/EPDCCH transmission to that UE. DM-RSsare associated with data signals and precoded prior to the transmissionwith the same precoder as data. A DM-RS can support up to 8 layers. Inaddition, as shown in FIG. 2, interference between the reference signalsmay be avoided by applying mutually orthogonal patterns, referred to asOrthogonal Cover Codes (OCC), to pairs of consecutive reference symbols.

Channel State Information Reference Signals (CSI-RSs) are anotherexample of a DL RS. CSI-RSs are intended to be used by UEs to acquireCSI configured in transmission modes 9 and 10 (as shown in Table 1) forchannel-dependent scheduling, link adaptation, and multi-antennatransmissions. Compared to a CRS, a CSI-RS has a lower time/frequencydensity (e.g., transmitted every 5 ms to 80 ms), thereby implying lessoverhead and a higher degree of flexibility compared to thecell-specific reference signals. Moreover, the CSI-RS will support up to8 antenna ports by LTE release 12 (shown in FIG. 3) and up to 16 antennaports by release 13.

With respect to antenna ports, 3GPP TS 36.211, Evolved Universal RadioAccess (E-UTRA), Physical channels and modulation (Release 13) (referredto hereinafter as “TS 36.211”), describes that:

-   -   An antenna port is defined such that the channel over which a        symbol on the antenna port is conveyed can be inferred from the        channel over which another symbol on the same antenna port is        conveyed. There is one resource grid per antenna port.

In general, LTE symbols that are transmitted via identical antenna portsare subject to the same channel conditions. In order to determine thecharacteristic channel for an antenna port, separate reference signalsmay be defined for each antenna port.

With respect to CSI-RSs, TS 36.211, Evolved Universal Radio Access(E-UTRA), Physical channels and modulation (Release 13), V13.1.0,defines Table 2 below and describes that:

-   -   CSI reference signals are transmitted on one, two, four, eight,        twelve, or sixteen antenna ports using p=15, p=15,16, p=15, . .        . , 18, p=15, . . . , 22, p=15, . . . , 26 and p=15, . . . , 30,        respectively. For CSI reference signals using more than eight        antenna ports, N_(res) ^(CSI)>1 CSI-RS configurations in the        same subframe, numbered from 0 to N_(res) ^(CSI)−1, are        aggregated to obtain N_(res) ^(CSI)N_(ports) ^(CSI) antenna        ports in total. Each CSI-RS configuration in such an aggregation        corresponds to N_(ports) ^(CSI)∈{4,8}.

TABLE 2 Aggregation of CSI-RS Configurations Number of antenna Totalnumber of ports per CSI-RS Number of CSI-RS antenna ports configurationconfigurations N_(res) ^(CSI)N_(ports) ^(CSI) N_(ports) ^(CSI) N_(res)^(CSI) 12 4 3 16 8 2

The reference-signal sequence r_(l,ns)(m) is defined by 3GPP TS 36.211:

$\begin{matrix}{{{r_{l,{ns}}(m)} = {{\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {2m} \right)}}} \right)} + {j\frac{1}{\sqrt{2}}\left( {1 - {2 \cdot {c\left( {{2m} + 1} \right)}}} \right)}}},{m = 0},{{1\ldots N_{RB}^{DL}} - 1}} & (1)\end{matrix}$

where n_(s) is the slot number within radio frame and l is theOrthogonal Frequency Division Multiplexing (OFDM) symbol number withinthe slot. The pseudo-random sequence c(n) is defined in section 7.2 ofTS 36.211.

The pseudo-random sequence generator shall be initialized with

c _(init)=2¹⁰·(7·(n′ _(s)+1)+l+1)·(2·N _(ID) ^(CSI)+1)+2·N _(ID) ^(CSI)+N _(CP)  (2)

at the start of each OFDM symbol where

$\begin{matrix}\begin{matrix}{n_{s}^{\prime} = \left\{ \begin{matrix}{{10\left\lfloor {n_{s}/10} \right\rfloor} + {n_{s}\ {mod}\; 2\mspace{14mu}{for}\mspace{14mu}{frame}\mspace{14mu}{structure}\mspace{14mu}{type}\mspace{14mu} 3}} \\{n_{s}\ {otherwise}}\end{matrix} \right.} & \;\end{matrix} & (3) \\{N_{CP} = \left\{ \begin{matrix}{1\ {for}\mspace{14mu}{normal}\ {CP}} \\{0\ {for}\mspace{14mu}{extended}\ {CP}}\end{matrix} \right.} & (4)\end{matrix}$

Continuing with example DL reference signals, Positioning ReferenceSignals (PRSs) were introduced in LTE release 9 to enhance LTEpositioning functionality. In particular, PRSs support the use of UEmeasurements on multiple LTE cells to estimate the geographical positionof a given UE.

Turning now to uplink reference signals, similar to LTE DL, referencesignals are also used in LTE UpLink (UL). LTE defines UL DemodulationReference Signals (DM-RSs) and UL Sounding Reference Signals (SRSs). ULDemodulation Reference Signals (DM-RSs) are used by the base station forchannel estimation for coherent demodulation of the Physical UplinkShared CHannel (PUSCH) and the Physical Uplink Control CHannel (PUCCH).In LTE, DM-RS are only transmitted within the RBs specifically assignedfor PUSCH/PUCCH transmission and span the same frequency range as thecorresponding physical channel. UL Sounding Reference Signals (SRS) areused by the base station for CSI estimation for supporting uplinkchannel-dependent scheduling and link adaptation. An SRS may also beused for the base station to obtain CSI estimation for DL under the caseof channel reciprocity.

With respect to CSI feedback in LTE, DL channel-dependent scheduling isa key feature of LTE, which selects the DL transmission configurationand related parameters depending on the instantaneous DL channelcondition, including the interference situation for example. To supportthe DL channel-dependent scheduling, a given UE provides the CSI to theevolved Node B (eNB). The eNB uses the information for its schedulingdecisions. The CSI may consist of one or more pieces of information,such as, a rank indication (RI), a precoder matrix indication (PMI), ora channel-quality indication (CQI). The RI may provide a recommendationon the transmission rank to use, or may provide a number of preferredlayers that should be used for PDSCH transmission to the UE. The PMI mayindicate a preferred precoder to use for PDSCH transmission. The CQI mayrepresent the highest modulation-and-coding scheme to achieve ablock-error probability of 10%, for example at most. Together, acombination of the RI, PMI, and CQI forms a CSI feedback report to theeNB. The information included in the CSI report may depend on the UE'sconfigured reporting mode. For example, in some cases, RI and PMI do notneed to be reported unless the UE is in a spatial multiplexingmulti-antenna transmission mode.

In Long term Evolution (LTE), multi-antenna techniques are used toachieve improved system performance, including improved system capacity(more users per cell), improved coverage (possibility for larger cells),and improved service provisioning (e.g., higher per-user data rates).The availability of multiple antennas at the transmitter and/or thereceiver can be utilized in different ways to achieve differentobjectives. For example, multiple antennas at the transmitter and/or thereceiver can be used to provide antenna diversity against fading on theradio channel. Multiple antennas at the transmitter and/or the receivercan be used to “shape” the overall antenna beam in a certain way, whichcan be referred to as antenna beamforming. For example, antennabeamforming can be used to maximize the overall antenna gain in thedirection of the target receiver or to suppress specific dominantinterfering signals. Multiple antennas can be used for antenna spatialmultiplexing, which refers to the simultaneous availability of multipleantennas at the transmitter and receiver to be used to create multipleparallel communication “channels” over the radio interface. Antennaspatial multiplexing can provide high data rates within a limitedbandwidth, which is referred to as Multiple-Input and Multiple-Output(MIMO) antenna processing.

Turning now to downlink control information (DCI), DCI refers to apredefined format in which the DCI is formed and transmitted in aPhysical Downlink Control Channel (PDCCH). The DCI format informs the UEhow to get its data that is transmitted on a Physical Downlink SharedChannel (PDSCH) in the same subframe. It carries the details for the UEsuch as, for example, number of resource blocks, a resource allocationtype, a modulation scheme, a redundancy version, a coding rate, etc.,which help the UE find and decode the PDSCH from the resource grid.There are various DCI formats used in LTE in PDCCH, and exampledifferent DCI formats are included in Table 3 below

TABLE 3 Example DCI Formats DCI Format Usage Major Contents Format 0 ULGrant. Resource RB Assignment, Transmit Allocation for UL Data PowerControl (TPC), PUSCH Hopping Flag Format 1 DL Assignment for Single- RBAssignment, TPC, Input and Single-Output Hybrid Automatic Repeat (SISO)Request (HARQ) Format 1A DL Assignment for SISO RB Assignment, TPC,(compact) HARQ Format 1B DL Assignment for MIMO RB Assignment, TPC, withRank 1 HARQ, PMI Format 1C DL Assignment for SISO RB Assignment (minimumsize) Format 1D DL Assignment for Multi RB Assignment, TPC, User MIMOHARQ, DL Power Offset Format 2 DL Assignment for Closed RB Assignment,TPC, Loop MIMO HARQ, Precoding Information Format 2A DL Assignment forOpen RB Assignment, TPC, Loop MIMO HARQ, Precoding Information Format 2BDL Assignment for RB Assignment, TPC, Transmission Mode 8 HARQ,Precoding (Dual layer beamforming) Information Format 2C DL Assignmentfor RB Assignment, TPC, Transmission Mode 9 HARQ, Precoding InformationFormat 3 TPC Commands for PUCCH Power Control Only and PUSCH with 2 bitpower adjustment Format 3A TPC Commands for PUCCH Power Control Only andPUSCH with 1 bit power adjustment Format 4 UL Assignment for UL RBAssignment, TPC, MIMO (up to 4 layers) HARQ, Precoding Information

An example DCI format is illustrated in Table 4, which contains fieldsfor DCI format 2.

TABLE 4 DCI Format 2 Field Name Length (Bits) Resource allocation header1 Resource block assignment for resource 6 (1.4 MHz) allocation Type 0 8(3 MHz) 13 (5 MHz) 17 (10 MHz) 19 (15 MHz) 25 (20 MHz) Subset N/A (1.4MHz) 1 (3 MHz) 1 (5 MHz) 2 (10 MHz) 2 (15 MHz) 2 (20 MHz) Shift N/A (1.4MHz) 1 (3 MHz) 1 (5 MHz) 1 (10 MHz) 1 (15 MHz) 1 (20 MHz) Resource blockassignment for resource N/A (1.4 MHz) allocation Type 1 6 (3 MHz) 13 (5MHz) 14 (10 MHz) 16 (15 MHz) 22 (20 MHz) TPC for PUCCH 2 DownlinkAssignment Index 2 HARQ Process 3 (FDD) 4 (TDD) Transport block tocodeword swap flag 1 Modulation and Coding Scheme (MCS) for 5 TransportBlock 1 New Data Indicator (NDI) for Transport 1 Block 1 RedundancyVersion (RV) for Transport 2 Block 1 MCS for Transport Block 1 5

Referring generally to FIG. 4, with respect to three-dimensional (3D)beam systems (which can also be referred to as beamforming systems), a3D beam system (e.g., 3D beam system 400) can explore both horizontaland elevation (vertical) angles. In addition, 3D beamforming can achievea better degree of freedom as compared to traditional 2D beamformingsystems that only consider horizontal angles. The 3D beamforming systemuses Active Antenna System (AAS) technology to adjust antenna weights ofhorizontal antenna ports and also the antenna elements in the verticaldirection. Referring in particular to FIG. 4, an example 3D beam 402 canbe characterized by a beam emission direction 404 and a beamwidth ΔB.The beam emission direction 404 can be described by a horizontal angle406 and an elevation angle 408, where ψ represents the horizontal angleand θ represents the elevation angle of the beam 402. The beamwidth ΔBindicates how wide the 3D beam 402 can span. In practice, a 3D beam isdistinguished by its 3 dB beamwidth. Thus, to summarize, a 3D beam canbe characterized by the parameters of horizontal angle, elevation angle,and beamwidth 9, ΔB). As shown, the emission direction 404 can bedistinguished by the horizontal angle 406 (in the x and y plane) and theelevation angle (in the x and z plane).

Turning now to Full-Dimension (FD) Multiple-Input and Multiple-Output(MIMO), FD-MIMO typically includes a base station with a two-dimensionalantenna array that supports multi-user joint elevation and azimuthbeamforming. This will result in higher cell capacity compared toconventional systems in release 12. Recent study has shown that withFD-MIMO techniques, LTE systems can achieve 3-5× performance gain cellcapacity and cell edge throughput.

As stated above, LTE has introduced CSI-RS, which can be used for DLchannel CSI estimation for all the UEs. There are up to 8 antenna portsspecified in release 10 and up to 16 antenna ports specified in release13. The CSI-RS design principal is one of the bases for 3D MIMO systems.

It is recognized herein that current LTE reference signals may beinadequate for future cellular (e.g., New Radio) systems.

SUMMARY

Configurable reference signals are described herein. In an exampleembodiment, an apparatus can obtain a reference signal configuration,wherein the reference signal configuration comprises time and/orfrequency resources allocated for a reference signal. The referencesignal configuration may further comprise spatial resources allocatedfor the reference signal. Further, the apparatus can transmit thereference signal in accordance with the reference signal configuration,such that at least one device obtains information from the referencesignal. The time resources associated with the reference signal mayinclude at least one of a start time at which the reference signal isallocated, a number of time intervals during which the reference signalis allocated, a time pattern at which the reference signal is allocated,or an indication of whether the reference signal is periodic. In anexample, the reference signal configuration is a function of one or morecharacteristics associated with the time intervals. The frequencyresources associated with the reference signal may include at least oneof a start frequency at which the reference signal is allocated, anumber of subcarriers in which the reference signal is allocated, afrequency pattern at which the reference signal is allocated, and/orwith an indication of a frequency hopping pattern. The reference signalconfiguration may include one or more functions performed by thereference signal, and the one or more functions may include controlchannel demodulation, data channel demodulation, interferencemeasurement, channel state information measurement, radio resourcemanagement measurement, beam sweeping, beamform training, time andfrequency offset tracking, or synchronization.

It is also recognized herein that as the number of transmit antennas insystems (e.g., NR systems) increases, the reference signal (RS) overheadmay increase to unacceptable levels. Embodiments described hereinprovide an enhanced and more efficient design for Channel StateInformation Reference Signals (CSI-RS) as compared to currentapproaches.

In one embodiment, an apparatus comprises a processor, a memory, andcommunication circuitry. The apparatus is connected to a network, forinstance a new radio (NR) network, via its communication circuitry. Theapparatus further comprises computer-executable instructions stored inthe memory of the apparatus which, when executed by the processor of theapparatus, cause the apparatus to perform operations. For example, theapparatus can obtain context information corresponding to one or moreterminals. Based on the context information, the apparatus can definespot areas for covering by one or more 3D beams. The apparatus canassign one or more 3D beams to respective spot areas. Based on theassignment, the apparatus can identify 3D beams that are non-adjacentwith respect to one other, and the apparatus can send the 3D beams thatare identified as non-adjacent with respect to one another to therespective spot areas using the same antenna port. Further, based on thecontext information, the apparatus can define at least one null spotarea within which no terminal is present, and the apparatus can assignno beam to the null spot area. In one example, based on the assignment,the apparatus identifies 3D beams that are adjacent to one another, andsends the 3D beams that are identified as adjacent to each other viadifferent antenna ports. The apparatus may obtain context informationcorresponding to one or more terminals by periodically receivinggeographic data from the one or more terminals. The geographic data maybe indicative of a physical location of the respective terminal. The 3Dbeams may comprise Channel State Information Reference Signals (CSI-RS),and the antenna ports may comprise CSI-RS ports. Further, the apparatusdescribed above may be part of a radio access network. For example, theapparatus may be part of an eNodeB or an eNodeB like entity.

In another example embodiment, an apparatus can, based on locationinformation associated with each of a plurality of mobile devices, forma first wide beam that is sent to an area within a cell. The apparatuscan receive a report from each of one or more mobile devices within thearea, each report indicating an optimal wide beam associated with therespective mobile device. Based on the received reports, the apparatuscan group select mobile devices of the one or more mobile devices into afirst cluster, and send the first wide beam to the first cluster,wherein the optimal wide beam associated with the select mobile devicesmay be the first wide beam. Further, the apparatus can receive anindication, from one or more of the select mobile devices in the firstcluster, of a second wide beam that is associated with a second clusterof mobile devices. The indication can identify the second wide beam asan interference beam, and there may be more than one interference beam.Thus, the apparatus can send the first wide beam and the second widebeam to the first and second clusters, respectively, using differentantenna ports. Further still, when no indication that identifies a thirdwide beam as an interference beam is received from any of the mobiledevices in the first cluster, the apparatus can send the first and thirdwide beams to first and third clusters, respectively, using the sameantenna port.

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key features oressential features of the claimed subject matter, nor is it intended tobe used to limit the scope of the claimed subject matter. Furthermore,the claimed subject matter is not limited to limitations that solve anyor all disadvantages noted in any part of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

A more detailed understanding may be had from the following description,given by way of example in conjunction with accompanying drawingswherein:

FIG. 1 depicts an example Cell-Specific Reference Signal (CRS)allocation per resource block.

FIG. 2 depicts an example Demodulation Reference Signals (DM-RS)allocation per resource block.

FIG. 3 depicts an example Channel State Information Reference Signal(CSI-RS) allocation per resource block.

FIG. 4 depicts an example 3D beam.

FIG. 5 depicts an example high data rate (indoor) use case in which oneor more embodiments can be implemented.

FIG. 6 depicts an example high density use case in which one or moreembodiments can be implemented.

FIG. 7 illustrates different numerologies mixed with differentbandslices, in accordance with an example.

FIG. 8 depicts example use cases for embodiments described herein.

FIG. 9 depicts example reference signal (RS) configurations fordifferent numerologies.

FIG. 10 depicts an example RS that is shared by multiple time intervals.

FIG. 11 depicts an example RS that is shared with adjacent timeintervals.

FIG. 12 depicts example RS configurations for different time intervalshaving different lengths.

FIG. 13 depicts example RS configurations for time intervals having thesame length.

FIG. 14 illustrates an example RS configuration for the demodulation ofcontrol channel(s) for different numerologies.

FIG. 15 illustrates an example dedicated RS configuration for thedemodulation of control channels.

FIGS. 16A and 16B illustrate an example beamforming reference signal(BF-RS) for Initial Access.

FIGS. 17A and 17B depict an example BF-RS configuration for datatransmission beam pairing.

FIGS. 18A and 18B is a call flow for an example On-demand RSConfiguration/Reconfiguration in accordance with an example embodiment.

FIGS. 19A and 19B is a call flow for an example On-demand RSConfiguration/Reconfiguration implemented within a centralizedarchitecture in accordance with another example embodiment.

FIG. 20 is a diagram of an example Graphical User Interface (GUI) inaccordance with an example embodiment.

FIG. 21 depicts an example CSI-RS allocation per subframe.

FIG. 22 is a call flow that shows an example fixed beam forming usingcontext associated with a user equipment (UE) in accordance with anexample embodiment.

FIG. 23 shows an example of non-adjacent 3D beams that can be formed bythe call flow of FIG. 22.

FIG. 24 is a 2D grid table of the non-adjacent 3D beams shown in FIG.23.

FIG. 25 shows an example of CSI-RS port reuse resource allocation thatis time division based in accordance with an example embodiment.

FIG. 26 shows an example of CSI-RS port reuse resource allocation thatis frequency division based in accordance with an example embodiment.

FIG. 27 is an example of non-adjacent (dynamic) 3D beam spots that canbe formed in accordance with an example embodiment.

FIG. 28 is a call flow that illustrates an example of beam spotallocation that can form the beam spots illustrated in FIG. 27.

FIG. 29 shows an example of CSI-RS port reuse resource allocation thatis time division based in accordance with an example embodiment.

FIG. 30 shows an example of CSI-RS port reuse resource allocation thatis frequency division based in accordance with an example embodiment.

FIG. 31 shows an example graphical user interface that is associatedwith a UE in accordance with an example embodiment.

FIG. 32 shows an example system in which there are wide beams as Tier 1beams and narrow beams as Tier 2 beams in accordance with an exampleembodiment.

FIG. 33 is a call flow that shows an example of how inter-cluster CSI-RSbeams and intra-cluster CSI-RS beams can be formed in accordance with anexample embodiment.

FIG. 34 shows an example of a widebeam (WB) CSI-RS resource allocationin accordance with an example embodiment.

FIG. 35 is a 2D grid table that shows an example of Tier 2 Beam CSI-RSresource allocation with inter-cluster CSI-RS reuse.

FIG. 36 shows an example of port class formats for KP-based CSI-RS withsize 2 in accordance with an example embodiment.

FIG. 37 shows an example of port class formats for beamformed CSI-RSwith size 2 in accordance with an example embodiment.

FIG. 38 is a call flow for CSI-RS with neighbor port reduction inaccordance with an example embodiment.

FIG. 39 is a flow diagram for selecting a port class format inaccordance with an example embodiment.

FIG. 40 shows an example of CSI-RS port reuse resource allocation thatis KP-based for a full channel estimation in accordance with an exampleembodiment.

FIG. 41 shows another example of a KP-based CSI-RS port reuse resourceallocation in accordance with an example embodiment.

FIG. 42 shows an example of a beamformed CSI-RS port reuse resourceallocation for a full channel estimation in accordance with an exampleembodiment.

FIG. 43 shows another example of a beamformed CSI-RS port reuse resourceallocation in accordance with an example embodiment.

FIG. 44 is a diagram that illustrates an example front loaded DM-RSpattern with multiple ports.

FIG. 45 is a diagram that illustrates an example DM-RS placement incenter symbols of a transmission time.

FIG. 46 is a diagram that illustrates an example DM-RS for highermobility scenarios spread over time.

FIG. 47A illustrates an example of sharing between two subframes of thesame user.

FIG. 47B illustrates an example of sharing between sub-frames of twodifferent users who are precoded the same way.

FIG. 48 is a diagram that illustrates an example of two bundled PRBsthat undergo the same precoding but have different DM-RS patterns.

FIG. 49 is a diagram that illustrates an example tracking referencesignal (TRS) that is assigned in specific resources across the availablebandwidth.

FIG. 50A depicts an example in which no TRS is allocated.

FIG. 50B depicts an example in which multiple resources are allocatedfor a TRS in frequency.

FIG. 50C depicts an example in which a higher density of a TRS isassigned in time.

FIG. 51 is a diagram that illustrates example sub-bands with differentnumerologies for a Sounding Reference Signals (SRS).

FIG. 52 is a diagram that illustrates an example fixed numerology forSRS resources.

FIG. 53A illustrates one embodiment of an example communications systemin which the methods and apparatuses described and claimed herein may beembodied.

FIG. 53B is a block diagram of an example apparatus or device configuredfor wireless communications in accordance with the embodimentsillustrated herein.

FIG. 53C is a system diagram of an example radio access network (RAN)and core network in accordance with an example embodiment.

FIG. 53D is another system diagram of a RAN and core network accordingto another embodiment.

FIG. 53E is another system diagram of a RAN and core network accordingto another embodiment.

FIG. 53F is a block diagram of an exemplary computing system 90 in whichone or more apparatuses of the communications networks illustrated inFIGS. 53A, 53C, 53D and 53E may be embodied.

FIG. 54 is a diagram that illustrates an example SRS signaled withdifferent numerologies with reserved resources in a given time durationT.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

As an initial matter, 3D Multiple-Input and Multiple-Output (MIMO) canbe referred to as 5G MIMO or new radio (NR) MIMO herein, withoutlimitation.

It is recognized herein that a straightforward approach for implementing3D MIMO would be to assign one Channel State Information (CSI) ReferenceSignal (RS) (CSI-RS) port per each transmit antenna element. It isfurther recognized herein that in this approach, however, the number oftransmit antennas at a base station will be limited by the availablenumber of CSI-RS ports and by the available resource elements in thetime-frequency resource block, which might not be possible from thepractical system design and standardization points of view with largernumber of antennas at the base station. Currently, there are twoapproaches for a CSI-RS design for Full Dimension (FD) MIMO (FD-MIMO) tosupport up to 16 antenna ports: beamformed CSI-RS and non-precodedCSI-RS schemes, which are now described by way of background.

With respect to current approaches to beamformed CSI-RS, in order toacquire relatively accurate 3D MIMO channel estimation and CSI, CSI-RSsymbols transmitted on the transmit antenna elements in every column areprecoded with the elevation beam weighting vector. Hence, for eachelevation beam, only one CSI-RS port is assigned to the transmit antennaelements in one column. All the horizontal ports are used and differentCSI-RS ports are used by different columns. Each column is precoded witha weighting vector to form the desired elevation beam.

For example, with respect to elevation beam 1, the CSI-RS symbolstransmitted on transmit elements in the first column are precoded withweighting vector W₍₁₎ ^(v) and the same procedure with the sameweighting vector is applied to the second column of transmit antennaelements. Thus, if there are N_(h) horizontal ports, the procedure willbe repeated until the last column. Then for elevation beam 2, the CSI-RSwill be precoded with a different weighting vector W₍₂₎ ^(v). The sameprocedure will be repeated for elevation beam 2 and for the remainingelevation beams. Thus, each elevation beam will have a different CSI-RSconfiguration that uses different CSI-RS ports/REs per the RBtransmitting CSI-RS. Assuming there are Q elevation beams, then Q×N_(h)number of CSI-RS ports/REs are required to transmit the CSI-RS for theFD-MIMO systems described above.

Thus, in some FD-MIMO systems, for each elevation beam, one CSI-RS portis assigned to the transmit antenna elements in one column. The CSI-RSsymbols transmitted on the transmit antenna elements in one column areprecoded with a weighting vector forming the desired elevation beam. Forthe elevation beam W₍₁₎ ^(v), a UE will search for its horizontalprecoding matrix W₍₂₎ ^(v) and calculate the Channel Quality Indication(CQI). Procedures are repeated for each elevation beam. A UE willmeasure one or more beamformed CSI-RS resources. In some cases, theoptimal elevation beam can be selected as the one with the maximum CQI.The UE can report the beams' channel information to the eNB or selectthe optimal beam and report the beam index and corresponding CSI to theeNB using CSI reporting mechanisms. CSI reporting, such as CQI and/orPMI and RI, is associated with the selected beam(s).

With respect to current approaches to non-precoded CSI-RS, which canalso be referred to as Kronecker-Product (KP) based CSI framework,KP-based CSI-RS is based on the assumption that the 3D channel H_(3D)between an eNB and a UE can be approximated by the KP between theazimuth and elevation domain channels H_(h) and H_(v), respectively,

H _(3D) ≈H _(h) ⊗H _(v)  (5)

where w_(h) and w_(v) are the precoding vectors for the azimuth andelevation domains respectively, and w_(3D) w_(h)⊗w_(v) is a KP-basedprecoder. Thus, the effective channel will be:

H _(3D) w _(3D)≈(H _(h) ⊗H _(v))(W _(h) ⊗W _(v))=(H _(h) w _(h))⊗(H _(v)w _(v))  (6)

The CSI-RS ports are transmitted on elements in the vertical andhorizontal axes of the array. A UE can be configured with multiple CSIprocesses—one associated with the azimuth CSI-RS resource and anotherassociated with the elevation CSI-RS resource. These CSI processes areused for obtaining precoder information for the azimuth and theelevation dimensions separately from the UE. At the eNB, the azimuth andthe elevation precoder information is used to form a 2D precoder with aKronecker structure. As an example, a 64-port precoder can be formed atthe eNB from CSI feedback comprising of an 8-port precoding feedback inazimuth and 8-port precoding feedback in elevation. Thus, with respectto the KP-based CSI-RS scheme, the total number of CSI-RS ports requiredis equal to N_(h)+N_(v)−1, as compared to N_(h)N_(v) when using thestraightforward approach.

It is recognized herein that the number of transmit antennas at the basestation may be increased, for example, to 32 antenna ports or greater.Further, beamformed CSI-RS and non-precoded CSI-RS may improve theabove-summarized schemes to support more antenna ports. Further, withrespect to 5G systems, it is possible that a significantly increasednumber of antennas may be implemented at the base station to furtherincrease cell capacity, for example, by 10× performance gain. Forexample, an eNB may use antenna arrays with a few hundred antennassimultaneously serving many UEs in the same time-frequency resource.Without being bound by theory, in an example massive MIMO system, as thenumber of the transmit antennas increases to infinity (very large),cross-correlation of two random channel realizations decreases to zero,and there will be no multi-user interference resulting fromco-scheduling and multiple access. This may greatly improve the systemthroughput, and it may be energy-efficient, secure, robust, andefficient (e.g., use spectrum efficiently), which makes massive 3D MIMOa potentially key enabler for 5G cellular systems.

Turning now to NR frame structure, subframes may be self-contained, suchthat a subframe may contain control information for a grant, data, andan A/N acknowledgement. Further, a self-contained subframe may haveconfigurable UL/DL/side link allocations and reference signals withinits resources. In some cases, a time interval X (e.g., Interval-X) maycontain one or more of the following, presented by way of example andwithout limitation, a DL transmission part, a guard, and an ULtransmission part. The DL transmission part of the time interval X maycontain downlink control information, downlink data transmissions,and/or reference signals. The UL transmission part of time the intervalX to may contain uplink control information, uplink data transmissions,and/or reference signals.

With respect to NR beamformed access, it is recognized herein thatcharacteristics of the wireless channel at higher frequencies may besignificantly different from the sub-6 GHz channel on which the LTEnetwork is currently deployed. It is further recognized herein that itmay be a challenge to design the new Radio Access Technology (RAT) forhigher frequencies while overcoming this larger path-loss. In additionto this larger path-loss, the higher frequencies are subject tounfavorable scattering environment due to blockage caused by poordiffraction. Therefore, it is recognized herein that MIMO/beamformingmay be critical to guaranteeing sufficient signal level at the receiverend.

In some cases, relying solely on digital precoding to compensate for theadditional path-loss in higher frequencies might not be enough toprovide similar coverage as below 6 GHz. Thus, the use of analogbeamforming for achieving additional gain can be an alternative inconjunction with digital precoding. The sufficiently narrow beam may beformed with many antenna elements, which is likely to be quite differentfrom the one assumed for the LTE evaluations. For large beamforminggain, the beam-width correspondingly tends to get reduced, and hence thecoverage beam with the large directional antenna gain might cover theentire horizontal sector area, specifically in 3-sector configurationfor example.

Thus, in some cases, multiple transmissions in the time domain withnarrow coverage beams steered to cover different serving areas might benecessary. The analog beam of a subarray can be steered toward a singledirection on each OFDM symbol, and thus the number of subarrays maydetermine the number of beam directions, and the corresponding coverageon each OFDM symbol. The provision of multiple narrow coverage beams forthis purpose can be referred to as “beam sweeping.” For analog andhybrid beamforming, the beam sweeping may be critical to provide thebasic coverage in NR. In some cases, for analog and hybrid beamformingwith massive MIMO for example, multiple transmissions in the time domainwith narrow coverage beams steered to cover different serving areas maybe critical to cover the entire coverage areas within a serving cell inNR.

3GPP TR 38.913 defines scenarios and requirements for New Radio (NR)technologies. Example Key Performance Indicators (KPIs) that imposerequirements, which may be relevant to embodiments described herein, foreMBB, URLLC and mMTC devices are summarized in Table 5 below.

TABLE 5 Example KPIs for eMBB, URLLC and mMTC Devices Device KPIDescription Requirement eMBB Peak data Peak data rate is the highesttheoretical data rate which 20 Gbps for rate is the received data bitsassuming error-free conditions downlink and assignable to a singlemobile station, when all 10 Gbps for assignable radio resources for thecorresponding link uplink direction are utilized (i.e., excluding radioresources that are used for physical layer synchronization, referencesignals or pilots, guard bands and guard times). Mobility Mobilityinterruption time means the shortest time 0 ms for intra- interruptionduration supported by the system during which a user system timeterminal cannot exchange user plane packets with any mobility basestation during transitions. Data Plane For eMBB value, the evaluationneeds to consider all 4 ms for UL, Latency typical delays associatedwith the transfer of the data and 4 ms for packets in an efficient way(e.g. applicable procedural DL delay when resources are notpre-allocated, averaged HARQ retransmission delay, impacts of networkarchitecture). URLLC Control Control plane latency refers to the time tomove from a 10 ms Plane battery efficient state (e.g., IDLE) to start ofLatency continuous data transfer (e.g., ACTIVE). Data Plane For URLLCthe target for user plane latency for UL 0.5 ms Latency and DL.Furthermore, if possible, the latency should also be low enough tosupport the use of the next generation access technologies as a wirelesstransport technology that can be used within the next generation accessarchitecture. Reliability Reliability can be evaluated by the successprobability 1-10⁻⁵ of transmitting X bytes ⁽¹⁾ within 1 ms, which is thewithin 1 ms. time it takes to deliver a small data packet from the radioprotocol layer 2/3 SDU ingress point to the radio protocol layer 2/3 SDUegress point of the radio interface, at a certain channel quality (e.g.,coverage- edge). NOTE1: Specific value for X is FFS. mMTC Coverage“Maximum coupling loss” (MCL) in uplink and 164 dB downlink betweendevice and Base Station site (antenna connector(s)) for a data rate of[X bps], where the data rate is observed at the egress/ingress point ofthe radio protocol stack in uplink and downlink. UE Battery UserEquipment (UE) battery life can be evaluated by 15 years Life thebattery life of the UE without recharge. For mMTC. UE battery life inextreme coverage shall be based on the activity of mobile originateddata transfer consisting of [200 bytes] Uplink (UL) per day followed by[20 bytes] Downlink (DL) from Maximum Coupling Loss (MCL) of [tbd] dB,assuming a stored energy capacity of [5 Wh]. Connection Connectiondensity refers to total number of devices 10⁶ devices/km² Densityfulfilling specific Quality of Service (QoS) per unit area (per km²).QoS definition should take into account the amount of data or accessrequest generated within a time t_gen that can be sent or receivedwithin a given time, t_sendrx, with x % probability.

As described further below, embodiments described herein may help enableenhanced mobile broadband (eMBB). Example deployment scenarios for eMBBinclude, indoor hotspots, dense urban areas, rural areas, urban macroareas, and high speed areas. An indoor hotspot generally refers to asmall coverage area per site/TRP (Transmission and Reception Point) andhigh user throughput or user density in buildings. Key characteristicsof this deployment scenario include high capacity, high user density,and consistent user experience.

A dense urban microcellular deployment scenario generally focuses onmacro TRPs with or without micro TRPs. A dense urban area generallyrefers to an area with high user densities and traffic loads, such as inin city centers and other dense urban areas. Key characteristics of thisdeployment scenario include high traffic loads, outdoor coverage, andoutdoor-to-indoor coverage. A rural deployment scenario generallyfocuses on larger and continuous coverage. Key characteristics of thisscenario include continuous wide area coverage and supporting high speedvehicles. An urban macro deployment scenario generally focuses on largecells and continuous coverage. Key characteristics of this scenarioinclude continuous and ubiquitous coverage in urban areas. With respectto high speed areas, it is recognized herein that there will be agrowing demand for mobile services in vehicles, trains, and aircrafts.While some services are the natural evolution of the existing ones(e.g., navigation, entertainment, etc.), some others representcompletely new scenarios, such as broadband communication services oncommercial aircrafts (e.g., by a hub on board). The degree of mobilityrequired will depend upon the specific use case. In one example usecase, speeds may be greater than 500 km/h.

Another example deployment scenario is urban coverage for massiveconnection. The urban coverage for massive connection scenario generallyfocuses on large cells and continuous coverage for massive machine typecommunications (mMTC). Key characteristics of this scenario includecontinuous and ubiquitous coverage in urban areas, with very highconnection density of mMTC devices. This deployment scenario may applyto the evaluation of the Key Performance Indicator (KPI) of connectiondensity. As yet another example, a highway deployment scenario focuseson scenarios in which vehicles are traveling on roadways at high speeds.Key performance indicators (KPIs) evaluated under this scenario includereliability/availability at high speeds/mobility (and thus frequenthandover operations). Yet another example deployment scenario is urbangrid for connected car, which focuses on highly densely deployedvehicles placed in urban areas. For example, this scenario may includefreeways that lead through an urban grid. An example KPI evaluated underthis scenario is reliability/availability/latency in high network loadand high UE density situations.

Referring now to FIG. 5, an example use case is depicted for an eMMBindoor scenario (e.g., office or residence) that focuses on smallcoverage area per beam or Transmission and Reception Point (TRP), andhigh number of 3D MIMO beams for user throughput or user density inbuildings. Key characteristics of this deployment scenario may includehigh capacity, high user density, and consistent user experience indoorswith stational or nomadic mobility. Therefore, the 3D MIMO beams may bestatic or slow changing as shown in FIG. 5.

Referring also to FIG. 6, an example use case is depicted for an eMMBoutdoor or outdoor-to-indoor scenario that focuses on the transport of ahigh volume of data traffic per area (traffic density) or on thetransport of data for a high number of connections (connection density),which may require a high number of 3D MIMO beams in the deployment. Keycharacteristics of this deployment scenario may include high volume andhigh capacity upload and download data, and high user density, forexample, which may depend on time (e.g., morning, evening, weekday,weekend etc.) and location (e.g., pedestrians in shopping mall, downtownstreet, stadium; users in buses in dense city center, etc.). This usecase may include stationary objects or nomadic indoor mobility or veryslow (e.g., pedestrians) mobility or outdoor mobility (e.g., of cars).Therefore, the 3D MIMO beams may be more dynamically distributed (ascompared to FIG. 5) as shown in FIG. 6.

In the current 3GPP LTE system, it is recognized herein that currentreference signal design creates problems for an NR system. Some of theseissues are now summarized below at a high level for purposes of example.In some cases, reference signals introduced undesirable time andfrequency resource overhead. Current reference signals might not supportNR function requirements, such as beam sweeping and beamforming trainingfor example. Further, it is recognized herein that existing approachesto reference signals do not support different numerologies mixed withina flexible frame structure.

With respect to time and resource overhead, current LTE has fixedperiodic reference signals, such as CRS and CSI-RS for example, and nomatter whether the system needs the reference signals or not, thereference signals are always ON. Further, current LTE has dedicatedreference signals for a specific function such as, for example,demodulation reference signals (DM-RS) for data channel demodulation,CSI-RS for CSI measurement, etc. In some cases, current LTE hasreference signals that occupy the entire frequency bandwidth, such asCRS and CSI-RS for example. Further, in some cases, the referencesignals are redundant. It is also recognized herein that theabove-described overhead issues may be amplified in an NR system becausethe NR system may support more antennas as compared to an LTE system.

In addition, current LTE reference signal schemes do not supportdifferent numerologies for supporting different devices or services(e.g., eMBB, URLLC, and mMTC) with different band slices (e.g.,numerology sub-bands), as shown in FIG. 7. For example, it is recognizedherein that current LTE reference signals may fail the low latencyrequirement for URLLC devices, which may require very low latency insome cases (e.g., 0.5 ms of data plane latency). It is recognized hereinthat issues related to supporting different mixed numerologies may applyto various, for instance all, NR scenarios/use cases, such as thoseshown in FIG. 8.

Embodiments are now described that address issues related to providingreference signals that are configurable, such that NR systems can bemore efficient and flexible. In an example embodiment, reference signalsare allocated to support different numerologies and different RSfunctions. In an example, a reference signal configuration includes timeand frequency resources for a reference signals. Example time resourcesassociated with the reference signal may include at least one of a starttime at which the reference signal is allocated, a number of timeintervals during which the reference signal is allocated, a time patternat which the reference signal is allocated, an indication of whether thereference signal is periodic, or the like. Example frequency resourcesassociated with the reference signal may include at least one of a startfrequency at which the reference signal is allocated, a number ofsubcarriers (or groups) in which the reference signal is allocated, afrequency pattern at which the reference signal is allocated, anindication of a frequency hopping pattern, or the like. Further, aspatial domain allocation may be configured for a beamformed RS, asdiscussed further below.

Referring now to FIG. 9 an example NR-RS allocation for mixednumerologies is shown. The example reference signals are allocated fordifferent subbands, as indicated by the numbers in FIG. 9. For instance,RS1 corresponds to subband 1, and RS2 corresponds to subband 2, etc. Itwill be understood that five reference signals are shown for purposes ofexample, but embodiments are not limited to the illustrated example. Asshown, each reference signal may have a corresponding configuration,which may include time (t), frequency (f), and spatial (s) resources.Further, each RS may be applicable to different numerologies withdifferent subcarrier spacings and symbol length. In accordance with theillustrated embodiment, example subcarrier spacings include wide,medium, and narrow subcarrier spacings. For example, as shown, RS1 (t1,f1, s1) represents the configurable RS that is allocated for a widesubcarrier spacing numberology in only subband 1, which has a certainfrequency hopping pattern and lasts N1 time intervals. As indicated inthe FIG. 9, the allocations with respect to the time and frequencydomains may be configured. For example, the scaling in the time domainbetween two RS resource elements (REs) may be configured as i symbols,and the scaling in the frequency domain between two RS REs may beconfigured as j subcarriers. In addition, in an example, an RSconfiguration may represent a contiguous RE configuration in time orfrequency, such as, for example, RS2 (t2, f2, s2) allocatedcontinguously within a number of subcarriers in frequency (FIG. 9).

As described herein, an NR-RS (or simply RS) may be dedicated to anumerology or common to multiple numerologies. In some cases, withrespect to each numerology per subband, an RS allocation may bedifferent, for example, in terms of frequency resources, time resources,spatial resources, time duration in number of time intervals(represented as Interval-X in FIG. 9), frequency duration, or frequencyhopping pattern. In some cases, with respect to multiple numerolgies insingle or multiple subbands, RS allocations may be the same as eachother, for example in a common configuration for multi-numerology toserve a particular function to reduce the system overhead.

A reference signal configuration may have one or more configurablefields, such as the example fields listed in Table 6. One or more (forinstance all) of the fields may be used to configure a given RS. In somecases, each configuration may include multiple RS allocations, which maybe applied to different types of reference signals such as, for example,demodulation reference signals (DM-RS) or channel state informationreference signals (CSI-RS). Further, the multiple RS allocations may beapplied to different time and frequency resources for the same RS type.A subcarrier group, such as the physical resource block (PRB) (group of12 subcarriers) can be used. The resource allocation in a givenfrequency domain may be measured by the number of j subcarriers in Table6 below.

TABLE 6 Example Configurable NR-RS Fields Field Element Meaning of eachField NumRSTypes Number of configured RS types (e.g., 2 types as shownwherein for purposes of example) RSType1 Function of RS such as DM-RS,CSI-RS NumerologyIndex Numerology type (for common RS allocation permulti-numerology, the index will be more than 1 value)TransmissionDirection DL RS or UL RS StartTime Start time of allocationTimeAllocation Number of n Interval-X's per allocation, where n >= 1integer TimeAllocationPattern Time Allocation Pattern such as one RS REper i (i >= 1) OFDM symbols within an Interval-X or other unevenlydistributed patterns. StartFreqency Start frequency of allocationFrequencyAllocation Number of m (m >= 1) subcarrier groups perallocation FreqAllocationPattern Frequency Allocation Pattern such asone RS RE per j (j >= 1) sub carriers or other unevenly distributedpatterns Periodicity trs duration if periodic allocation or 0 ms ifaperiodic allocation FreqHoppingPattern Frequency hopping patternRSType2 Function of RS such as DMRS, CSIRS NumerologyIndex Numerologytype (for common RS allocation per multi-numerology, the index will bemore than 1 value) TransmissionDirection DL RS or UL RS StartTime Starttime of allocation TimeAllocation Number of n Interval-X's perallocation, where n >= 1 integer TimeAllocationPattern Time AllocationPattern such as one RS RE per i (i >= 1) OFDM symbols within anInterval-X or other unevenly distributed patterns. StartFreqency Startfrequency of allocation FrequencyAllocation Number of m (m >= 1)subcarrier groups per allocation FreqAllocationPattern FrequencyAllocation Pattern such as one RS RE per j (j >= 1) sub carriersPeriodicity trs duration if periodic allocation or 0 ms if aperiodicallocation FreqHoppingPattern Frequency hopping pattern . . .

With respect to wide subcarrier spacing numerology, to achieve lowlatency requirement, an RS may be allocated at the beginning of both theDL duration and UL duration per a time interval X. If frequency hoppingis applied, for example, the NR-RS may be allocated at the beginning ofboth DL duration (e.g., DL RS) and UL duration (e.g., UL RS) per timeinterval X per frequency hopping pattern, as illustrated by RS1 in FIG.9. In another example, a RS that is allocated at the beginning of agiven time interval X may be shared by multiple time intervals. This maybe applicable to low speed scenarios, such as shown in FIG. 10, whereinthat one allocation of a RS is shared by three time intervals. It willbe understood that this example is not limited to a wide subcarrierspacing numerology. Referring now to FIG. 11, in yet another example,with respect to wide subcarrier spacing numerology, an RS may beallocated to be shared among adjacent time intervals, for example,because of a short time interval X and/or a lack of symbol resources.

The length of a given time interval X for NR may be variable, and withineach time interval X, the DL and UL durations may also be varied. Insome cases, even with the same length of time interval X, the containednumber of symbols and sub-carriers may also be distinct. Therefore, inone embodiment, the RS may have different configurations for a differenttime interval X, and the configuration may be a function of the lengthof the time interval X, as shown in FIG. 12. In another example, angiven RS may have different configurations for DL and UL durations, andthe configuration may be a function of the length of DL time durationper the time interval X, or the length of UL time duration per the timeinterval X. In another example, a given RS configuration may be afunction of the number of symbols and the number of subcarriers per agiven time interval X. In some cases, an RS configuration may be variedamong time intervals that are the same, as shown in FIG. 13. Thus, asdescribed above, a reference signal configuration may be a function ofone or more characteristics associated with the time intervals of thereference signal.

Reference signals may serve different functions, and thus the referencesignal configurations described herein may include one or more functionsperformed by the respective reference signal. In some cases, regardlessof whether an RS is for UL or DL, it may be configured for multiplefunctions such as, for example and without limitation, control channeldemodulation, data channel demodulation, interference measurement, CSImeasurement, radio resource management (RRM) measurement, beam sweeping,beamform training, time and frequency offset tracking, orsynchronization. Thus, a given RS allocation may be statically,semi-statically, or dynamically configured to serve different functions.In one example, a given RS configuration serves a single function. Inanother example, a given RS configuration serves multiple functions(e.g., interference measurement and CSI measurement, or beam trainingand RRM measurement), for example, to enhance system resource efficiencyfor NR.

With respect to control channel demodulation, in an example, an RS maybe configured at the leading symbols of the DL/UL duration of each timeinterval X for the function of demodulation of DL/UL control channels.In some cases, the RS is on-demand with DL/UL control channels only, andvaries per numerology. In some cases, the RS is shared among multiplenumerologies or dedicated to different numerologies. FIG. 14 depicts anexample of how to configure and allocate common subband demodulation RSfor control channels for mixed numerologies, in accordance with anexample embodiment. As shown, the RS REs may be spaced by j subcarriers.FIG. 15 shows an example of how to configure and allocate dedicateddemodulation RS for control channels for mixed numerologies, inaccordance with an example embodiment.

With respect to a data channel demodulation, reference signals may havedifferent configurations for demodulation of DL/UL data transmissions ascompared to configurations for demodulation of DL/UL control channels.In an example, the RS may be on-demand with DL/UL data transmissionsonly, and may be different per numerology. FIG. 12 shows an example ofthe RS configured for demodulation of DL and UL data transmissions. Itwill be understood that other configurations are not excluded.

With respect to CSI measurement, the RS may be configured for CSImeasurement and a CSI feedback report, which, in some cases, may requireno more than one CSI-RS RE per antenna port. In some cases, on accountof the large number of antenna ports in NR systems, the NR CSI-RS may bein an aperiodic mode to reduce the resource overhead. In other cases,depending on the use case, the NR CSI-RS may be configured to be in aperiodic mode. A reference signal for CSI measurement may benon-precoded based and/or beamformed based. The beamformed RS mayrequire more resource overhead as compared to the non-precoded RS. Thebeamformed RS may be configured in an aperiodic mode and may be moreUE-specific as compared to the non-precoded RS. In an example, thenon-precoded RS can be configured in a periodic mode, and theperiodicity may be configurable based on different use cases, trafficloads, mobility, etc.

With respect to TDD systems, due to channel reciprocity, DL CSImeasurement may use the channel estimation from UL RS information. Thus,the RS configuration for CSI measurement may be less frequently, oraperiodically, configured in this case.

With respect to reference signals for beam sweeping, the RS may bepredefined for beam sweeping for initial access, such as, for example,for physical broadcasting signals, synchronization signals, systeminformation for downlink, and random access signals for uplink. A RSthat serves for this beam sweeping function can be referred to herein asa Beam Formed RS (BF-RS). In an example, an NR node or a TRP may conductbeam sweeping over all individual transmit beams to cover the wholearea. In some cases, the TRP may be the same as the Radio Resource Head(RRH) in the existing LTE architecture. FIGS. 16A and 16B show anexample BF-RS configuration in which eight beams cover the entire areawithout resource reuse. In an example, the BF-RS may be predefined as afunction of beam width, or a number of beams per NR-Node TRP, or UE. Inan example with a total of 32 beams, the BF-RS may require 32 BF-RS REs(e.g., if there is no RE reuse among beams) per a beam sweeping cycle.The BF-RS may be allocated at the beginning of each beam sweeping periodand distributed proportionately across the bean sweeping duration. In anexample, the BF-RS may be predefined to use subband allocation. A givenBF-RS RE/port may require k (where k is a fraction of a RE or one ormore REs) REs (e.g., antennas) per beam. Different beams may usedifferent antenna ports when transmitting at the same time. If differentbeams are transmitted at different times, the same antenna port may beused. In another example, the BF-RS may also use multiple REs/multipleantenna ports per beam. In this case, the number of REs and ports may beconfigured. It will be understood that FIGS. 16A and 16B show an exampleBF-RS allocation, but the BF-RS of a beam may be allocated with multipleREs per symbol per beam, or may be allocated with the entire subband REsper symbol per beam.

With respect to BF-RS orthogonality, for an example narrow beamconfiguration, especially for a higher frequency band, the BF-RSrequirement for orthogonality may be reduced due to high directionalityper transmitter-receiver beam pair. In this case, multiple beams may betransmitted via the same time/frequency/spatial resource to reduce thesystem overhead. For example, beam 1˜beam m may use the same time andfrequency resource, and similarly, beams (m+1)˜beam 2m, beam (2m+1)˜beam3m . . . may use the same time and frequency resource. To furtherclarify by way of example, beam (m+1) refers to a beam number of m+1.With respect to an example wide beam configuration, BF-RS orthogonalitymay also be required. Thus, to achieve the BF-RS orthogonality, variousmechanisms may be implemented, such as, for example, time divisionmultiplexing, frequency division multiplexing, code divisionmultiplexing or (orthogonal cover code) (OCC), or spatial divisionmultiplexing. For example, if beam 1 and beam k are spatially separatedfrom each other, the same time and frequency resource may be used totransmit beam 1 and beam k. In some cases, the BF-RS may be predefinedto use either continuous or discontinuous resources/symbols in one timeinterval or multiple time intervals. For example, an NR node maypredefine M symbols/REs per time interval, and configure N timeintervals to cover one beam sweeping cycle. In this example, the totaltime resources used per beam sweeping cycle is M*N symbols.

In another example, the BF-RS may be predefined with dedicated resourcesper numerology, or configured with common resources for allnumerologies. In the common resources example, the UEs with differentnumerologies can search a common resource region for initial access ofbeam sweeping. The common resources may save the system resources andreduce resource overhead. Beam sweeping may be conducted in both DL andUL directions. For TDD systems with channel reciprocity of DL and UL,the beam sweeping for uplink may be simplified or skipped. The BF-RS mayinclude primary system information. Example of such information mayinclude information similar to information captured in MIB/SIB1/SIB2 ofan LTE system. Without the primary information, a given UE might not beable to access the system. The BF-RS may also include secondary systeminformation, which refers to system information other than the primarysystem information. The BF-RS may also include synchronization signals.In an example, the configuration of the primary system information BF-RSand the configuration of the synchronization signals BF-RS may bepredefined so that the UE can process this information before accessingthe system. For example, the UE may be pre-provisioned with the relevantconfiguration parameter (e.g. using Over-the-Air provisioning) or theconfiguration parameters may be preloaded onto the UE. Alternatively,these configuration parameters may be specified in a specification fordifferent modes of operations. In an example, the configurationparameters of the secondary system information BF-RS may be delivered tothe UE using system information broadcasts or dedicated signaling.

With respect to reference signals for beamforming training of datatransmission beam pairings, in accordance with an example, an RS may beconfigured as a UE-specific RS. The RS for beamforming training may beon-demand, for example in response to UE's feedback that includesbeamforming training request, in response to a UE's UL controlsignaling, or in response to an event trigger at an NR node or the TRP.For a particular UE, multiple beams may be used based on beamformingtraining measurement results. With respect to beam width for datatransmissions, in some cases, the beams for data transmissions may bethe same beam width as the initial access beams. Then for a particularUE or a group of UEs, the transmitter and receiver may choose a subsetof beams upon which to implement beam refinement and alignment.Referring to FIGS. 17A and 17B, for example, with respect to aparticular UE or a group of UEs, an NR Node or TRP may choose beams 1,2, 3 and 4 (B1, B2, B3, B4) to do beamforming training for datatransmissions. It will be understood that while FIGS. 17A and 17B showan example BF-RS allocation for beamforming training, the BF-RS of abeam may be allocated with multiple REs per symbol per beam, allocatedfor the entire subband of REs per symbol per beam as desired. In anotherexample, the beam for data transmissions may have a different beam width(e.g., more narrow) as compared to the initial access beam. For aparticular UE or a group of UEs, the transmitter and receiver may choosea subset of narrower beams to do beam refinement and beam selection. Thenarrower beams may be the beams spatially close to the initial accessbeam direction. For example, for a particular UE or a group of UEs, theNR-Node or TRP may choose narrower beams 11, 12, 13, and 14 to dobeamforming training. Beams 11, 12, 13, 14 may be the narrower beamsthat spatially close to/covered by the initial access beam 1 direction.

With respect to beamformed/precoded reference signals, such as the BF-RSfor beamforming training, the RS allocation may consider the spatialdivision as configurable parameters. One or more of the followingexample fields in Table 7 may be used to configure the BF-RS via onemethods described herein below.

TABLE 7 Example Configurable NR Beamformed RS Fields Field ElementMeaning of each Field NumRSTypes Number of RS types RSType1 Function ofRS such as BF-RS Function Function of RS, such as beam sweeping or CSImeasurement or multiple functions NumTotalBeams Total number of beamsper beam sweeping or beamforming training NumBeams Number of beams perRS configuration (e.g. may conduct beamforming training with a subset ofbeams) BeamPattern Beam index allocation per RE, such as beam ID y at(ti, fj) BeamReuseFactor Number of beams reused per RE BeamReusePatternHow to spatially reuse the beam RE, such as beam ID y, y + 3, y + 6using the same RE NumerologyIndex Numerology type (for common RSallocation per multi-numerology, the index will be more than 1)TransmissionDirection DL RS or UL RS StartTime Start time of allocationTimeDuration Number of time intervals per allocationTimeAllocationPattern Time Allocation Pattern such as one RS RE per MOFDM symbols StartFreq Start frequency of allocation FrequencyDurationNumber of subbands/subcarriers per allocation FreqAllocationPatternFrequency Allocation Pattern such as one RS RE per j sub carriersPeriodicity K ms if periodic allocation or 0 ms if aperiodic allocationFreqHoppingPattern Frequency hopping pattern (0 for no frequencyhopping) . . .

With respect to reference signals for RRM measurement, a multi-functionRS can be used for RRM measurement. FIGS. 18A and 18B depict an exampleof a multi-function RS for RRM measurement. Referring to FIGS. 18A and18B, an example system 1800 is shown which includes a plurality of UEs(UE1, UE2, UEm and UEm+1) and an NR node 1802 (or TRP 1802). It will beappreciated that the example system 1800 is simplified to facilitatedescription of the disclosed subject matter and is not intended to limitthe scope of this disclosure. Other devices, systems, and configurationsmay be used to implement the embodiments disclosed herein in additionto, or instead of, a system such as the system illustrated in FIGS. 18Aand 18B and all such embodiments are contemplated as within the scope ofthe present disclosure.

Referring to FIG. 18A, in accordance with the illustrated embodiment, at1804, the node 1802 unicasts a respective RS configuration to each ofthe UEs. Alternatively, at 1806, the node 1802 can broadcast an RSconfiguration to the UEs. The RS configuration may be the same for aplurality of the UEs. The RS configuration may also be different for aplurality of UEs. Thus, the RS configuration may be the same for someUEs and different for other UEs. At 1808, in accordance with theillustrated example, the node 1802 transmits the reference signals inaccordance with the respective reference signal configuration, such thatat least UE (device) obtains information from the reference signal. At1810, in accordance with the illustrated embodiment, the UE2 triggers anevent, such as beam changing for example. In response to the event, at1812, the UE2 sends an on-demand request to the node 1802. The requestmay include a request for a new RS configuration. At 1814, the node 1802reconfigures or updates an RS for the UE2, based on the request from theUE2. At 1816, the new RS configuration is sent to the UE2, in responseto the on-demand request.

Alternatively, referring to FIG. 18B, at 1818, one or more UEs maymonitor, for example, a CSI measurement, a beamforming measurement, anRRM measurement, or an interference measurement. At 1820, UEs maycollect respective measurements. At 1822, in accordance with theillustrated example, the node 1802 may reconfigure or update one or moreof the reference signal configurations. The reconfigurations of thereference signals may be based on, for example, a trigger or an event atthe node 1802, a given UE's feedback from its measurements, or changesto traffic load. Thus, a reference signal configuration orreconfiguration may be obtained in response to a trigger from at leastone device or the network, one or more measurements associated with atleast one device, or a traffic load on the network. The new RSconfiguration may be sent to one or more of the UEs based on thefeedback from 1820. In accordance with the illustrated example, at 1824,a new RS configuration is sent to the UE1 and the UEm. Unless otherwisespecified, a reference signal configuration may be a reconfiguration.

As mentioned above, with respect to reference signals for interferencemeasurements, a multi-function CSI-RS or a BF-RS may be configured forthe interference measurement function. Similarly, a multi-function RS(e.g., BF-RS or a CRS-like RS) may be configured for frequency and timetracking, or synchronization function.

As described above, a RS may serve as single function RS or amulti-function RS to reduce the system resource overhead. A given RS maybe configured differently for different functions. The RS configurationmay be dynamically changed as well as based on the function it performs,different numerologies, or different time intervals, for example.

Further, an RS may be configured for a specific UE or in anon-UE-specific mode. In a non-UE-specific mode, the RS may servemultiple, for instance all, UEs in a cell or in a coverage area of oneor more beams. Non-precoded CSI-RS and BF-RS for beam sweeping ofinitial access are examples of a possible multi-beam coverage scenario.Alternatively, an RS may be configured in a UE-specific mode withUE-specific allocation, such as, for example, a beamforming training RSfor data transmission beam pairing, or a beamformed CSI RS for CSImeasurement. Thus, a reference signal configuration may be allocated formultiple devices, such that a plurality of devices obtain informationfrom the reference signal, or a reference signal configuration may beallocated for a specific device, such that only one device obtainsinformation from the reference signal.

Further, in accordance with another example embodiment, referencesignals may be configured across levels (multi-level). For example, a RSmay be configured as level 1 with non-precoded CSI RS, and level 2 withbeamformed/precoded CSI RS for CSI measurement. By way of furtherexample, a RS may be configured as level 1 with wider beam RS forinitial access, and level 2 with narrower beam RS for data transmissionbeam pairing. Also, wider beam RS may be used, for example, for primarysystem information, while narrower beam RS may be used for the secondarysystem information. Each level may serve a distinct function. Each levelmay have different configurations, such as, for example, differentperiodicities or different allocations in time and frequency domain withdifferent durations.

As described above with reference to FIGS. 18A and 18B, a referencesignal may be configured on-demand. An on-demand RS may be triggered byan explicit UE request or autonomously by the network. The triggers inthe UE or the network may be one or more of the following, presented byway of example and without limitation:

-   -   Data in buffer with buffer report may trigger NR DMRS        configuration.    -   Service switching may trigger NR-RS reconfiguration to support        the changed service type/numerology more efficiently.    -   With UE movement, UE may request beamforming training procedures        with BF-RS reconfiguration to refine/realign the beam pair        between UE and NR-Node or TRP.    -   Increased/decreased data traffic loads may trigger NR-RS        reconfiguration with changed NR-RS density. For example, UEs        with less or no data traffic loads for a duration of time may        trigger the reconfiguration with less RS density to reduce        resource overhead and also to reduce the interference for        neighbor UEs and cells.    -   Based on various UE measurements.

Example UE measurements that may trigger an on-demand request for a newRS configuration include, CSI measurement and feedback, RRM measurementand feedback, Beamforming measurement and feedback, and Interferencemeasurement and feedback. Further, if a value changes within a UE'sfeedback report that corresponds to any of the above-mentionedmeasurements, a RS reconfiguration may be triggered. For example, CQI inthe CSI feedback report may change by K levels due to UE's movement orother reasons, which may trigger an RS reconfiguration for beamrepairing.

Referring again to FIGS. 18A and 18B, examples of on-demand RSreconfiguration are shown. In accordance with the illustrated example,decisions such as RS configuration, beamforming, and beam changing aremade by the node 1802 that is directly connected to the UEs. The node1802 can also connected to the UEs via a TRP/RRH, which can be referredto as a TRP controlled architecture or a distributed architecture.

Referring now to FIGS. 19A and 19B, an example centralized controlarchitecture 1900 is shown for on-demand RS reconfigurations. In thisexample, the UEs connect to the TPRs/RRHs 1902, but the TPRs/RRHs 1904do not have control capability. Thus, the information and the decisions,such as RS configuration, beamforming, and beam changing, are signaledthrough the TRPs/RRHs 1904 from/to a NR-Node/Central controller 1903to/from the UEs. It will be appreciated that the example architecture1900 is simplified to facilitate description of the disclosed subjectmatter and is not intended to limit the scope of this disclosure. Otherdevices, systems, and configurations may be used to implement theembodiments disclosed herein in addition to, or instead of, a systemsuch as the system illustrated in FIGS. 19A and 19B, and all suchembodiments are contemplated as within the scope of the presentdisclosure.

Still referring to FIGS. 19A and 19B, in accordance with the illustratedembodiment, at 1904, the node 1903 unicasts a respective RSconfiguration to each of the UEs through the TRPs/RRHs 1902.Alternatively, at 1906, the node 1903 can broadcast an RS configurationto the UEs through the TRPs/RRHs 1902. The RS configuration may be thesame for a plurality of the UEs. The RS configuration may also bedifferent for a plurality of UEs. Thus, the RS configuration may be thesame for some UEs and different for other UEs. At 1908, in accordancewith the illustrated example, the TRPs/RRHs transmit the referencesignals in accordance with the respective reference signalconfiguration, such that at least UE (device) obtains information fromthe reference signal. At 1910, in accordance with the illustratedembodiment, the UE2 triggers an event, such as beam changing forexample. In response to the event, at 1912, the UE2 sends an on-demandrequest to the node TRPs/RRHs 1902, which forwards the request to thenode 1903, at 1913. The request may include a request for a new RS. At1914, the node 1903 reconfigures or updates an RS for the UE2, based onthe request from the UE2. At 1915, the new RS configuration is sent toTRPs/RRHs 1902, which sends the new RS configuration to the UE2 (at1916), in response to the on-demand request.

Alternatively, still referring to FIG. 19, at 1918, one or more of theUEs may monitor, for example, a CSI measurement, a beamformingmeasurement, an RRM measurement, or an interference measurement. TheTRPs/RRHs 1902, at 1921, may collect the respective measurements fromthe UEs and send the feedback to the node 1903. At 1922, in accordancewith the illustrated example, the node 1903 may reconfigure or updateone or more of the reference signal configurations. The reconfigurationsof the reference signals may be based on, for example, a trigger or anevent at the node 1903, a given UE's feedback from its measurements, orchanges to traffic load. The new RS configuration may be sent to one ormore of the UEs based on the feedback from 1920. In accordance with theillustrated example, at 1923, the new RS configurations are sent fromthe node 1903 to the TRPs/RRHs 1902, which sends the respective RSconfigurations to the UE1 and the UEm (at 1924).

It is understood that the entities performing the steps illustrated inFIGS. 18 and 19 may be logical entities that may be implemented in theform of software (i.e., computer-executable instructions) stored in amemory of, and executing on a processor of, an apparatus configured forwireless and/or network communications or a computer system such asthose illustrated in FIGS. 53B and 53F. That is, the method(s)illustrated in FIGS. 18 and 19 may be implemented in the form ofsoftware (e.g., computer-executable instructions) stored in a memory ofan apparatus, such as the apparatus or computer system illustrated inFIGS. 53B and 53F, which computer executable instructions, when executedby a processor of the apparatus, perform the steps illustrated in FIGS.18 and 19. It is also understood that any transmitting and receivingsteps illustrated in FIGS. 18 and 19 may be performed by communicationcircuitry of the apparatus under control of the processor of theapparatus and the computer-executable instructions (e.g., software) thatit executes.

As described above, the configurable RS field elements may be configuredstatically, semi-statically, or dynamically. Also, as now described infurther detail, in accordance with various embodiments, reference signalconfigurations may be received: in system information via a broadcastchannel, via radio resource control signaling, in a medium accesscontrol (MAC) control element, or via a downlink control channel. BF-RSconfigurations may be predefined or pre-provisioned.

In an example, an RS configuration may be indicated by a SystemInformation Block (SIB). In an example, the supported time scale for RSreconfiguration may be every 640 ms or longer. UEs, for instance all UEsconnected to the NR-Node or TRP, may receive the system information.Thus, this method may be applicable to the static or semi-staticscenarios, and to a non-UE-specific RS configuration. Example RSconfiguration fields, shown below, can be carried by extending thecurrent SIB1, though it will be understood that the implementation ofsignaling RS configuration fields in the NR system is not limited tothis example.

SystemInformationBlockType1 message -- ASN1STARTSystemInformationBlockType1 ::= SEQUENCE { cellAccessRelatedInfoSEQUENCE { plmn-IdentityList PLMN-IdentityList, trackingAreaCodeTrackingAreaCode, cellIdentity CellIdentity, cellBarred ENUMERATED{barred, notBarred}, intraFreqReselection ENUMERATED {allowed,notAllowed}, csg-Indication BOOLEAN, csg-Identity CSG-Identity OPTIONAL-- Need OR }, cellSelectionInfo SEQUENCE { q-RxLevMin Q-RxLevMin,q-RxLevMinOffset INTEGER (1..8) OPTIONAL -- Need OP }, p-Max P-MaxOPTIONAL, -- Need OP freqBandIndicator FreqBandIndicator,schedulingInfoList SchedulingInfoList, tdd-Config TDD-Config OPTIONAL,-- Cond TDD si-WindowLength ENUMERATED { ms1, ms2, ms5, ms10, ms15,ms20, ms40}, systemInfoValueTag INTEGER (0..31), ...... NR-RS-Config-r1:: = SEQUENCE { RSType, NumerologyIndex, StartTime, TimeDuration,StartFreq, FreqDuration, Periodicity, NumBeams, BeamPattern,BeamReuseFactor, ...... }

In another example, RS configuration/reconfiguration may be performedvia Radio Resource Control (RRC) signaling. The corresponding time scalesupported by this example may depend on how fast the reconfiguration canbe performed. In some cases, an example time scale is about 200 ms. Inan example, there is one reconfiguration message per RRC connected user,unless a broadcast or a multicast approach is specified. TheRRCConnectionReconfiguration-NB message is the command to modify an RRCconnection. It may convey information for resource configuration(including RBs, MAC main configuration and physical channelconfiguration). The RS configuration fields can be carried by extendingthe current RRCConnectionReconfiguration-NB message as an example(example fields are shown below). However, the implementation ofsignaling RS configuration fields in the NR system is not limited tothis example below.

RRCConnectionReconfiguration-NB message -- ASN1STARTRRCConnectionReconfiguration-NB ::= SEQUENCE { rrc-TransactionIdentifierRRC-TransactionIdentifier criticalExtensions CHOICE { c1 CHOICE{rrcConnectionReconfiguration-r13RRCConnectionReconfiguration-NB-r13-IEs, spare1 NULL },criticalExtensionsFuture SEQUENCE { } } }RRCConnectionReconfiguration-NB-r13-IEs ::= SEQUENCE {dedicatedInfoNASList-r13 SEQUENCE (SIZE(1..maxDRB-NB-r13)) OFDedicatedInfoNAS OPTIONAL, -- Need ON radioResourceConfigDedicated-r13RadioResourceConfigDedicated-NB- r13 OPTIONAL, -- Need ON fullConfig-r13ENUMERATED {true} OPTIONAL, -- Cond Reestab lateNonCriticalExtensionOCTET STRING OPTIONAL, nonCriticalExtension SEQUENCE { } OPTIONAL }NR-RS-Config-r1 ::= SEQUENCE { RSType, NumerologyIndex, StartTime,TimeDuration, StartFreq, FreqDuration, Periodicity, NumBeams,BeamPattern, BeamReuseFactor, ...... } -- ASN1STOP

In another example, a RS configuration/reconfiguration may be indicatedby Medium Access Control (MAC) Control Element (CE) signaling in the MACheader, with time scale of adaptation on the order of a few tens of msfor example. The RS configuration fields can be carried by extending thecurrent MAC CE as an example (example fields are shown below in Table8). However, the implementation of signaling RS configuration fields inthe NR system is not limited to this example.

TABLE 8 Example RS configuration fields in a MAC CE MAC CE Field NameMAC header Buffer size 1 Buffer size 2 . . . . . . RS type 1 Numerologyindex 1 Start time 1 Time duration 1 Start frequency 1 Frequencyduration 1 Periodicity 1 Num beams 1 Beam pattern 1 Beam reuse factor 1. . .

In yet another example, an RS configuration/reconfiguration may beindicated via a DL control channel. This example NR-RS supportsconfiguration/reconfiguration by physical layer design, with time scaleof adaptation on the order of N time intervals (time interval is definedas x ms in the NR). The NR-RS configuration can be explicitly indicatedby physical DL control channel or signal. In some cases, this examplemay provide the best flexibility and adaptation capability, given thesupport of smaller time scale for NR RS reconfiguration as compared tothe above-described examples. The RS configuration fields can be carriedby NR DL control channels as an example (example fields are shown belowin Table 9). It will be understood, however, that the implementation ofsignaling RS configuration fields in the NR system is not limited tothis example below.

TABLE 9 Example RS configuration fields DL control channels DCI FieldName MCS PMI confirmation for precoding . . . RS type 1 Numerology index1 Start time 1 Time duration 1 Start frequency 1 Frequency duration 1Periodicity 1 Num beams 1 Beam pattern 1 Beam reuse factor 1 . . .

Turning now to configurable reference signals to support beam sweepingand beamforming training, beamforming is a mechanism that is used by atransmitter and receiver to achieve necessary link budget for subsequentcommunication. Beam sweeping in NR may be suitable for the transmissionof common control signaling, physical broadcast channel, and RRMmeasurement. Here, the common control signaling may include thesynchronization signals, system information for downlink, and randomaccess channels for uplink.

With respect to conducting DL beam sweeping and beamforming training,beam sweeping may send a BF-RS with wider transmit beams or narrowertransmit beams. For example, if wider beams are used for beam sweeping,then beamforming training may form narrower beams and send the BF-RSwith a subset of narrower beams (e.g., the narrower beams within theregion of the wider beam for beam sweeping may be a good candidate ofsubset beams) to further train/refine the narrower beams for datatransmissions. Subsets of beams may be adjusted/reconfigured based onmovement of the UE. In an example, if narrower beams are used for beamsweeping, then beamforming training may be used for beam pair alignmentand adjustment for data transmissions.

In an example in which beam sweeping sends the BF-RS with narrowertransmit beams, the NR-Node or TRP may sweep through the transmit beamsor choose a subset of beams. For example, assuming there are 36 transmitbeams (beams 1-36), then for beam sweeping, the NR-Node or TRP maychoose beams ID with 1+k*m, where k is configurable and m=0, 1, 2, 3, .. . , (36/k)−1. In an example in which a subset of narrower beams areused for beam sweeping, then beamforming training may be conducted tosweep through the beams adjacent to the best sweeping beam. For example,if beam 4 is the best transmit sweeping beam, the beams 2-6 or 3-5 maybe used for beamforming training.

In an example, the receiver/UE beam sweeping is optional/configurable,and it may use quasi-omni-directional beams or wider beams for receiverbeam sweeping/training. In an example in which quasi-omni-directionalbeams are used as receiver beams, the sweeping cycle time may bereduced. During beamforming training, a subset of wider beams ornarrower beams may be used to choose the best receiver beam for datatransmissions. In an example in which wider beams are used as receiverbeams, during beam training, a subset of wider beams may be used forfurther beam alignment or a subset of narrower beams may be used forbeamforming training. In an example in which narrower beams are used asreceiver beams, during beamforming training, a subset of narrower beamsmay be used for further beam alignment. Alternatively, the beamformingtraining may be skipped.

With respect to UL beam sweeping and beam training, in light of channelreciprocity in TDD systems, it is recognized herein that UL beamsweeping and beamforming training may be skipped or simplified to reducethe resource overhead, in some cases. In some cases, in can be assumedthat the NR-Node or TRP has the same transmit and receive beams, and thesame assumption can be made for respective UEs. In FDD systems, the ULbeam sweeping and beamforming training may be optional. When beamsweeping and beamforming training are in an ON mode, based on the DLbeam sweeping procedure results, the UL beam sweeping might not need todo full beam sweeping using all beams. In another example, the UL beamsweeping can perform whole coverage beam sweeping.

Beam sweeping may send the BF-RS with wider transmit beams or narrowertransmit beams. In an example in which wider beams are used for beamsweeping, then beamforming training may form narrower beams and sweepthrough a subset of the narrower beams to further train the narrowerbeams for data transmission. If narrower beams are used for beamsweeping, then beamforming training procedure is mainly for beamalignment for data transmissions. If beam sweeping uses narrowertransmit beams, a given UE may sweep through all the transmit beams orchoose a subset of beams. For example, assuming there are 16 transmitbeams (Beams 1-16), then for beam sweeping, the NR-Node or TRP maychoose beams ID with 1+k*m, where k is configurable and m=1,2,3, . . . ,(16/k)−1. If a subset of narrower beams is used for beam sweeping, thenbeamforming training may be conducted to sweep through the beamsadjacent to the best sweeping beam. For example, if beam 4 is the besttransmit sweeping beam, the beams 2-6 or 3-5 may be used for beamtraining. The receiver/NR-Node or TRP beam sweeping may be optional, andit may use quasi-omni-directional beams or wider beams or narrower beamsfor receiver beam sweeping. If quasi-omni-directional beams are used asreceiver beams, the sweeping cycle time may be reduced. Duringbeamforming training, a subset of wider beams or narrower beams may beused to choose the best receiver beam for data transmissions. If widerbeams are used as receiver beams, during beamforming training, a subsetof wider beams may be used to further beam alignment, or a subset ofnarrower beams may be used to further beamforming training. If narrowerbeams are used as receiver beams, during beamforming training, a subsetof narrower beams may be used for further beam alignment, or thebeamforming training may be skipped.

Interfaces, such as Graphical User Interfaces (GUIs), can be used toassist users to control and/or configure functionalities related toconfigurable reference signals described herein. FIG. 20 is a diagramthat illustrates an interface 2002 that enables a user to permit (ordisallow) RS configuration. The interface 2002 also enables a user topermit (or disallow) RS Beam Sweeping and Beamforming configurations. Itwill be understood that interface 2002 can be rendered using displayssuch as those shown in FIGS. 53B and 53F described below. Further, itwill be understood that the interface 2002 can vary as desired.

Turning now to CSI-RS designs in particular for 3D MIMO, in the current3GPP system, a given user equipment (UE) performs the downlink (DL)channel quality estimation using the CSI-RS transmitted from the basestation. In LTE, an antenna port is defined in conjunction with areference signal. Up to release 12, each CSI-RS port is assigned to oneantenna element and the system can support up to 8 antenna ports asshown in the boxes numbered 0-7 in FIG. 21.

Because reference signals are assigned in an orthogonal manner, with astraightforward approach, it is recognized herein that CSI-RS overheadwill grow linearly with the number of antenna ports to control thequantization error. With respect to NR systems that may include amassive number of antennas, the antenna ports may include more than 16ports. For example, there may be 32, 64, 128, 256, etc. ports.Accordingly, it is recognized herein that the CSI-RS overhead/densitymay be very large. To illustrate, by way of example, with respect to thestraightforward approach (orthogonal approach using current 4Gnumerology), one CSI-RS port is assigned to one antenna element. If thenumber of transmit antennas is 64, then approximately 48% of resourceelement (RE) resources may be used per the resource block (RB) thattransmits the CSI-RS symbols, as illustrated in table 10. Usingnormalization, 9.6% of DL RE resources on average may be used forCSI-RS, which is a large overhead for the system. Therefore, it isrecognized herein that this straightforward approach might not bepractical in 5G (NR) systems, particularly in view of a potentiallymassive number of antennas used at the base station.

With respect to a KP-based CSI-RS scheme, if the number of transmitantennas is 64, then approximately 11.5% of RE resources will be usedper the RB that transmits the CSI-RS symbols, as illustrated in Table10. By normalization, 2.3% of DL RE resources on average will be usedfor CSI-RS. It is also recognized herein that as the number of transmitantennas in 5G systems increase, the RS overhead may increase.

With respect to an example beamformed approach to CSI-RS, if the numberof transmit antennas is 64, then approximately 36.4% of RE resourceswill be used per the RB that transmits the CSI-RS symbols, asillustrated in table 10. Using normalization, 7.3% of DL RE resources onaverage will be used for CSI-RS. As the number of transmit antennas in5G systems increase, it is recognized herein that the RS overhead mayincrease, which may create problems for 5G 3D MIMO systems, amongothers.

As the analysis above and in table 10 indicates, the CSI-RS overhead maybe large and unacceptable with massive 3D MIMO deployed in a system suchas a NR system illustrated in FIGS. 5 and 6. As described above, theCSI-RS may take out the DL resources for the data transmission(particularly for the beamformed CSI-RS approach), which may lead to asubstantial loss in the maximum data throughput. Thus, systems may failto meet eMBB data rate and density requirements, among others.

Embodiments described herein provide an enhanced and more efficientdesign for CSI-RS as compared to current approaches. For example, goodchannel estimation can be achieved while keeping the CSI-RS overhead anddensity reasonably low, which may be desired in 5G systems (amongothers) in which a large number of antenna ports might be used.

TABLE 10 CSI-RS Overhead Calculation Summary # of Normalized CSI- TotalCSI-RS Overhead CSI-RS # of RS REs available Overhead Rate (5 ms schemeN_(h) N_(v) Beams per RB REs per RB Rate periodicity) Orthogonal 8 8None 64 132  48% 9.6% scheme KP-based 8 8 None 15 132 11.5% 2.3% schemeBeamformed 8 8 6 48 132 36.4% 7.3% scheme

It is recognized herein that as the number of transmit antennas insystems (e.g., 5G systems) increase, the reference signal (RS) overheadmay increase to unacceptable levels. Embodiments described hereinprovide an enhanced and more efficient design for Channel StateInformation Reference Signals (CSI-RS) as compared to currentapproaches.

For example, in one embodiment, as described in detail below, CSI-RSports are reused for non-adjacent 3D beams in a fixed 3D beam system. Afixed 3D beam system can refer to a system in which: (1) each 3D beamdirection is semi-persistently or persistently fixed; and (2) each fixed3D beam does not emit to the same direction. In an example, fixed 3Dbeams are configured to optimize a radio access network's operations andresource allocations. In some cases, or each 3D beam, one CSI-RS port isassigned to the transmit antenna elements in one column. The CSI-RSsymbols transmitted on the transmit antenna elements in one column canbe precoded with a weighting vector forming the desired 3D beam. In somecases, each horizontal antenna may use one antenna port and one CSI-RSRE. Further, in some cases, each 3D beam may use all N_(h) horizontalantenna ports and use N_(h) REs per RB that transmits the CSI-RSsymbols. Thus, based on the above, the CSI-RS ports/REs can be reused bynon-adjacent 3D beams in accordance with an example embodiment. The UEmay select an optimal 3D beam as, for example, the one with the maximumCQI. The UE may report the selected 3D beam to an eNB, such as by usingCQI and/or PMI and RI.

Thus, in accordance with an example embodiment, a given fixed 3D beamsystem can maximize the reuse rate for the CSI-RS ports of at leastsome, for instance all, of the non-adjacent beams, which will reduce thebeamformed CSI-RS overhead. This may apply to various uses cases, suchas the high data rate eMBB described above, as applied to stationary ornomadic scenarios (e.g., offices, apartment buildings).

In accordance with another embodiment, as described in detail below,CSI-RS ports are reused for non-adjacent 3D beam spots in a dynamic beamspot system. A dynamic 3D beam system can refer to a system in which:(1) each 3D beam direction is dynamic and irregular; and (2) eachdynamic 3D beam does not emit to the same direction. With respect toirregular and dynamic 3D beams, beam spots can be defined based on theUEs' geographical location information (e.g., see spots (S)1, S2, S3,etc. in FIG. 27). A beam spot refers to the service area wherein one ormore beams cover.

In some cases, uplink (UL) sounding reference signal (SRS) informationis read and full channel reciprocity (e.g., for TDD systems) or partialchannel reciprocity (e.g., for FDD systems) is used for DL channelestimation (e.g., Angle of Departure (AoD), Angle or Arrival (AoA) perUE). Based on the aforementioned information, an eNB can assign one ormore 3D beams per beam spot. Each beam spot may have its own CSI-RSconfiguration based on the chosen 3D beam(s). For non-adjacent beamspots, in accordance with an embodiment, the same CSI-RS ports/REs maybe reused for reference signaling. Thus, in some cases, in the CSIfeedback report, the UEs might not need to report the beam index to theeNB because the beam spots have already been formed based on the SRSinformation at the eNB.

Thus, in accordance with the aforementioned embodiment, a dynamic 3Dbeam system may reuse the CSI-RS ports of all the non-adjacent beamspots, which will greatly reduce the beamformed CSI-RS overhead withmassive antennas in NR cellular systems.

Referring now to FIG. 22, in accordance with an example embodiment,CSI-RS Port Reuse may be implemented in a fixed 3D beam system, such asa system 2200 illustrated in FIGS. 22 and 23. As shown in FIG. 22, theexample system 2200 includes an eNB 2202, a MME 2204, and a plurality ofUEs, in particular UE1 and UE2. It will be appreciated that the examplesystem 2200 is simplified to facilitate description of the disclosedsubject matter and is not intended to limit the scope of thisdisclosure. Other devices, systems, and configurations may be used toimplement the embodiments disclosed herein in addition to, or insteadof, a system such as the system illustrated in FIG. 22, and all suchembodiments are contemplated as within the scope of the presentdisclosure. It will further be appreciated that reference numbers may berepeated in various figures to indicate the same or similar features inthe figures.

In some cases, context information, for example, velocity, service type,schedule, data rate, etc., which is associated with a UE, may be usedfor configuring the fixed 3D beams (shown in FIG. 23) to optimize aradio access network's operations and resource allocations. As shown inFIG. 22, at 2205, a UE (UE1) may add context information through a radioconnection request to the eNB 2202. For example, a Radio ResourceControl (RRC) Connection may be used to report the context informationto the eNB 2202. Alternatively, as shown at 2212, a UE (UE2) may addcontext information through a network connection request to the MobilityManagement Entity (MME) 2202. The eNB 2202 may also include theagreed-upon parameters, such as schedule or data rate, via its RRCConnection Setup to the UE1, at 2208. Based on the context informationthat is received from the UE1, the radio access network, for instancethe eNB 2202, may configure its 3D beams (at 2206). In accordance withthe illustrated example, the UE1 sends an RRC Connection Setup Completemessage at 2210.

With continuing reference to FIG. 23, in accordance with the alternativeexample, the MME 2204 sends an Attach Accept message to the UE2, at2214. At 2216, the MME 2204 sends the UE context information to the eNB2202. At 2218, based on the context information that is received fromthe UE2, the radio access network, for instance the eNB 2202, mayconfigure its 3D beams. The eNB 2202 may also include the agreed-uponparameters, such as schedule or data rate, via its RRC ConnectionReconfiguration message to the UE2, at 2210.

In response, at 2222, the UE2 sends an RRC Connection ReconfigurationComplete message to the eNB 2202.

In NR, it is recognized herein that a large number of beamformed CSI-RSmay be targeted for energy-efficient small areas, as shown in FIG. 23that depicts fixed 3D beams. Referring to FIG. 23, beams B21, B41, B13,and B33 are non-adjacent beams with respect one another; beams B11, B31,B23, and B43 are non-adjacent beams with respect to one another; beamsB12, B32, B24, and B44 are non-adjacent beams with respect to oneanother; and beams B22, B42, B14, B34 are non-adjacent beams withrespect to one another. In an example, these non-adjacent beams canreuse the same CSI-RS ports/REs per RB that transmits CSI-RS symbols. Insome cases, the total power may be equally shared by the overlappingCSI-RS symbols per RE. FIG. 24 is a two-dimensional grid that depictsthe grouping of the beams of FIG. 23. As shown, beams that are next toeach other define adjacent beams. For example, beam B22 has adjacentbeams of B11, B12, B13, B21, B23, B31, B32, and B33. As described above,two beams that have another beam in between them define non-adjacentbeams with respect to each other. For example, beams B11 and B31 arenon-adjacent beams with respect to each other, and beams B21 and B13 arenon-adjacent beams with respect to each other.

In an example, adjacent beams, for instance all adjacent beams that formCSI-RS reuse groups use different CSI-RS ports for CSI-RS signaling.Non-adjacent beams, which are spaced apart from each other, can use thesame CSI-RS ports for CSI-RS signaling, to reduce the CSI-RS overhead.FIG. 24 depicts one example reuse pattern, though it will be understoodthat more or less beams may be used as desired.

By way of example, assume there are 8 horizontal antenna ports, the RBdiagram in FIG. 25 shows an example of how to reuse and allocate theCSI-RS ports/REs for non-adjacent beams per RB. As shown, 8 horizontalantenna ports are used per beam. In accordance with the illustratedembodiment, non-adjacent beams (e.g., group 1: B11, B31, B23 and B43)are all reusing the same 8 CSI-RS REs, which are showing as fouroverlapping instances in FIG. 25, to efficiently enhance the currentCSI-RS design to reduce the CSI-RS overhead. Similarly, the othernon-adjacent beam groups: (B21, B41, B13, B33); (B12, B32, B24, B44);and (B22, B42, B14, B34), may reuse the same 8 CSE-RS Res. Note thatFIG. 25 assumes that a total of 16 CSI-RS ports are used for subframe mand the next 16 CSI-RS ports are allocated in the next subframe, whichis a time division based allocation approach. FIG. 26 shows a frequencydivision based CSI-RS allocation approach, in which the first 16 CSI-RSports are allocated in sub-frequency 1 and the next 16 CSI-RS ports areallocated in sub-frequency 2. It will be appreciated that otherallocation methods (e.g. aggregating all 32 ports in the same subframe)may be utilized as desired.

It is recognized herein that, in some cases, no matter how large theantenna array grows for NR MIMO systems, the number of non-adjacent beamgroups will not increase above 4 groups, which means that the number ofREs used for transmitting CSI-RS will not increase with the number ofantenna beams. It is further recognized herein that the number of beamsin each group may increase as the number of 3D beams grows, but that mayonly affect the number of overlapping port instances per RE. Therefore,by using the CSI-RS design described above, the CSI-RS ports/REs may bereused at a maximum rate in the most efficient way, thereby limitingCSI-RS overhead.

Turning now to CSI-RS Port Reuse for a Dynamic 3D Beam Spot System, FIG.27 depicts an example of dynamic 3D beam spots. As used herein, a beamspot refers to a service coverage area under one or more beams (most areunder one beam as shown in FIG. 27) and the beam spot areas may overlap.As shown, beams B16, B10, B7, and B5 are non-adjacent with respect toone another; beams B11 and B1 are non-adjacent with respect to oneanother; beams B13, B9, and B4 are non-adjacent with respect to oneanother; beams B12 and B3 are non-adjacent with respect to one another;and beams B14 and B2 are non-adjacent with respect to one another. Thenon-adjacent beams can reuse the same CSI-RS ports/REs per RB thattransmits CSI-RS symbols.

FIG. 27 also includes NULL beam spots S15 and S6. NULL beam spots refersto imagined beam spots which do not physically exist. That is, no UEsneed service in that spot area and no CSI-RS ports need to betransmitted to create the beam spots. Adjacent beam spots refer to beamspots that are next to each other. Adjacent beam spots may includeoverlapping coverage area with one another. As shown, beam spots S1, S2,S3, S4 and S5 are examples of adjacent beam spots. Non-adjacent beamspots refer to two or more beam spots that have another beam spot or aNULL beam spot in between one another. As shown in FIG. 27, beams spotsS2 and S8 are non-adjacent beam spots with respect to each other, and S5and S7 are non-adjacent beam spots with respect to each other.

Referring also to FIG. 28, an example system 2800 includes an eNB 2802and a plurality of UEs, in particular a UE1 in beam spot S1, a UE2 inbeam spot S1, a UEm in beam spot S2, and a UEm+1 in beam spot S2. Asshown, to form the beam spots in a cell with irregular and dynamic 3Dbeams, the terminals (e.g., UEs in FIG. 28) may report theirgeographical location information to the NR node or TRP (e.g., eNB 2802)periodically. It will be appreciated that the example system 2800 issimplified to facilitate description of the disclosed subject matter andis not intended to limit the scope of this disclosure. Other devices,systems, and configurations may be used to implement the embodimentsdisclosed herein in addition to, or instead of, a system such as thesystem illustrated in FIGS. 27 and 28, and all such embodiments arecontemplated as within the scope of the present disclosure. For example,the illustrated eNB 2802, and generally any eNB referred to herein, maybe implemented alternatively by an eNB-like entity (e.g., NR node, TRP,RRH, etc.), an apparatus that is part of a radio access network, or thelike.

Still referring to FIG. 28, in accordance with the illustrated example,at 2804, the eNB 2802 sends a positioning reference signal (PRS) to eachof the UEs. At 2806, each UE estimates its location using the PRS. Insome cases, as shown at 2806, the UEs can use the DL RS to report theirlocation information. The PRS can support the use of terminalmeasurements on multiple NR cells to estimate the geographical locationof the terminal. It will be understood that location information of a UEcan be obtained by the eNB 2802 as desired. For example, locationinformation can be obtained using GPS (by a UE) or UL control channelsor signaling. Thus, the illustrated PRS message is used as an example,and is not limiting. In addition, other context information associatedwith a given UE, such as user type (e.g., static or mobile), velocity (xkm/h), traffic/service type (e.g., video conferencing,gaming/entertainment, web browsing), traffic/service scheduling (e.g.,day time traffic, night time), etc., may be piggybacked in the ULmessages to help 3D beam formation and reference signal and datascheduling at the eNB 2802.

Based on the information associated with the UEs, at 2810, the eNB 2802can define the spot areas as illustrated in FIG. 27. In some cases, ifno terminals are measured in a spot area, such as S6 and S15 in FIG. 27,that area is defined as a NULL beam spot. To illustrate, as shown in theexample of FIG. 27, most of the beam spot areas are covered by one beam,such as S1 and S2; some are covered by more than one beam, such as S8;and some do not need coverage, such as S6. After the spot areas aredefined, then eNB may use full channel reciprocity feature (e.g., forTDD systems) or partial channel reciprocity (e.g., for FDD systems) toread UL SRS information for DL channel estimation. Based on the aboveinformation, the eNB can get full or partial channel information for aDL channel (e.g., Angle of Departure (AoD) and Angle or Arrival (AoA))per UE. In an example, the eNB performs joint elevation and azimuthbeamforming per beam spot. The eNB can assign one or more 3D beams perbeam spot. Each beam spot may have its own CSI-RS configuration based onthe chosen 3D beam(s).

Continuing with the example, for non-adjacent beam spots, the sameCSI-RS ports/REs can be reused for sending reference signals at 2812. Inan example, adjacent beam spots, for instance all adjacent beam spots,use different CSI-RS ports for sending reference signals 2812. Further,non-adjacent beam spots can use the same spots for sending referencesignals, as shown in FIG. 27. In some cases, regarding the CSI feedbackreports collected at 2814 and 2815 and sent to the eNB 2802 at 2816 and2817, the UEs do not need to report the beam index to the eNB 2802because the beam spots have already been formed based on the RPS and SRSinformation at the eNB 2802. It is recognized herein that the beam indexfield exists in the current beamformed CSI-RS scheme, and the CSIfeedback overhead for NR MIMO systems can be reduced.

Thus, as described above, an apparatus can obtain context informationcorresponding to one or more terminals. Based on the contextinformation, the apparatus can define spot areas for covering by one ormore 3D beams. The apparatus can assign one or more 3D beams torespective spot areas. Based on the assignment of the one or more 3Dbeams, the apparatus can identify 3D beams that are non-adjacent withrespect to one other, and the apparatus can send the 3D beams that areidentified as non-adjacent to one another to the respective spot areasvia the same antenna port. More than one group of 3D beams may beidentified, wherein each group is comprised of 3D beams that arenon-adjacent to one another, and each 3D beam within a group is sent torespective spot areas via the same antenna port. Further, based on thecontext information, the apparatus can define at least one null spotarea within which no terminal is present, and the apparatus can assignno beam to the null spot area. In one example, based on the assignmentof the one or more 3D beams, the apparatus identifies 3D beams that areadjacent to one another, and sends the 3D beams that are identified asadjacent to each other via different antenna ports. The apparatus mayobtain context information corresponding to one or more terminals byperiodically receiving geographic data from the one or more terminals.The geographic data may be indicative of a physical location of therespective terminal, such that the one or more 3D beams are assigned torespective spot areas that correspond to the respective physicallocations of the one or more terminals. Thus, the at least one null spotarea within which no terminal is present can be defined based on thegeographic data, and accordingly, no beam might be assigned to the nullspot area. The 3D beams may comprise Channel State Information ReferenceSignals (CSI-RS), and the antenna ports may comprise CSI-RS ports.Further, the apparatus described above may be part of a radio accessnetwork. For example, the apparatus may be part of an eNodeB or aneNodeB like entity, or a variation thereof.

By way of example, assume there are 8 horizontal antenna ports. The RBdiagram in FIG. 29 shows an example of how to reuse and allocate theCSI-RS ports/REs for non-adjacent beam spots per RB. As shown, 8horizontal antenna ports are used per 3D beam. In accordance with theillustrated example, non-adjacent beam spots (e.g., group 1: B1 and B11shown FIG. 27) are all using the same 8 CSI-RS REs, which are shown astwo overlapping port instances in FIG. 29, to efficiently enhance thecurrent CSI-RS design to reduce the CSI-RS overhead. Similarly, theother non-adjacent beam groups in FIG. 29 can re-use the same REs. Forexample, still referring to FIG. 29, beams B2, B8_1 and B14 show threeoverlapping instances; beams B3, B8_2 and B12 show three overlappinginstances; beams B4, B9 and B13 show three overlapping instances; andbeams B5, B7, B10 and B16 show four overlapping instances. Note that inFIG. 29 it is assumed that a total of 16 CSI-RS ports are used forsubframe m and the next 24 CSI-RS ports are allocated in the nextsubframe, which is a time division based allocation approach. FIG. 30shows an example of a frequency division based CSI-RS allocationapproach in which the first 16 CSI-RS ports are allocated insub-frequency 1 and the next 24 CSI-RS ports are allocated insub-frequency 2. It will be understood that other allocation techniquesmay be implemented as desired (e.g., aggregating all ports in the samesubframe).

It is recognized herein that the above-described embodiments allow the3D beam spots to be more dynamically formed based on the geographicallocation, velocity, and traffic information when a UE has low mobility.Further, the NULL beam spots can be formed to save the CSI-RS resourcesby avoiding sending any reference signals to the NULL beam spots. It isfurther recognized herein that, in some cases, no matter how large thenumber of antenna beams for 5G MIMO systems, the number of non-adjacentbeam groups might not vary much, which means that the number of REs usedfor transmitting CSI-RS might not increase. Therefore, by using theCSI-RS design described above that includes dynamic and irregular 3Dantenna beams, the CSI-RS ports/REs may be reused at a maximum rate inthe most efficient way, thereby limiting CSI-RS overhead.

Referring now to FIG. 31, an example graphical user interface (GUI) isshown. A UE may include the GUI shown in FIG. 31. As described above,there are one or more parameters that may be pre-configured by a user toenable the enhanced CS-RS design for NR 3D MIMO described above. Exampleparameters include, location, user type, velocity, traffic/service type,traffic/service scheduling, etc. A user of the UE can use theillustrated GUI to pre-configure the parameters that will be sent to anetwork node, for instance an eNB. It will be understood that the GUIcan be used to monitor, configure, and query alternative parameters asdesired. It will be further understood that the GUIs can provide a userwith various information in which the user is interested via a varietyof charts or alternative visual depictions.

Referring now to FIG. 32, another example is shown in which fixed 3Dbeams and dynamic 3D beams may be configured based on contextinformation associated with various UEs. Example context informationincludes location, velocity, and traffic information. The beams can beconfigured to optimize a radio access network's operations and resourceallocations. FIG. 32 illustrates an example procedure for configuringthe fixed 3D beams and depicts two exemplary mechanisms to add a UE'scontext. In one example, context is added through a radio connectionrequest to the eNB (e.g., Radio Resource Control (RRC)). In anotherexample, context is added through a network connection request to theMobility Management Entity (MME) (e.g., Attach). FIG. 33 shows anexample method for configuring the dynamic 3D beams, and the CSI-RSmechanism is also shown.

In another example embodiment, described in detail below, beamformedCSI-RS is improved with cluster specific features. It is recognizedherein that a cluster-specific CSI-RS transmission scheme withinter-cluster port reuse can improve the design of beamformed CSI-RS infuture cellular systems. An eNB or alternative radio access apparatuscan form Tier 1 Wide Beams (WBs) based on various UEs or mobile devicesgeographical location information. While the term eNB is often used forpurposes of example herein, it will be understood that embodiments arenot limited to an eNB, and alternative nodes, including nodes orapparatus that will assume new names in the future, may implementvarious embodiments described herein. In an example, an eNB may also usefull channel reciprocity feature (for TDD systems) or partial channelreciprocity (for FDD systems) to read UL SRS information for DL channelestimation. Then eNB can perform elevation and azimuth beamformingmeasurement per Tier 1 beam.

In another example described below, multiple Tier 1 beams may bereceived or detected by respective UEs. Each UE may calculate thechannel state information for multiple beams and, in some cases, selectthe optimal beam as the one with the maximum CQI. Each UE can report itsoptimal Tier 1 beam to the eNB, such as beam index, CQI and/or PMI andRI. The UEs that report the same optimal Tier 1 beam can be defined in acluster. In an example, only one Tier 1 beam is assigned to one cluster.In another example, also based on the channel state information, ifgiven UE detects a plurality of wide beams, the UE may identify at leastone of the plurality of wide beams that it detected as an interferencebeam. The UE may also report the one or more interference beams to aradio access node (e.g., the eNB) if a given interference beam'sreceived power is larger than a predefined threshold. These reports canhelp determine inter-cluster interference at the eNB.

As described below, CSI-RS ports/REs can be reused for sending referencesignals of Tier 1 beams. For example, with respect to inter-cluster Tier1 beams, if interference Tier 1 beams are reported, which implies thatthere is high inter-cluster beam interference, the inter-cluster Tier 1beams cannot use the same CSI-RS ports. For inter-cluster Tier 1 beams,in some cases, all Tier 1 beams except the Tier 1 beams reported as theinterference Tier 1 beams may reuse the same CSI-RS ports for sendingreference signals. The eNB may then conduct beamformed CSI-RS for Tier 2Narrow Beams (NBs) within the assigned Tier 1 beam per cluster. This isreferred to herein as cluster-specific CSI-RS. For inter-cluster beams,the same CSI-RS ports/REs can be reused for sending reference signals ofTier 2 beams. In an example, all intra-cluster Tier 2 beams usedifferent CSI-RS ports for sending reference signals. For inter-clusterTier 2 beams, if interference Tier 1 beam are reported, thecorresponding inter-cluster Tier 2 beams cannot use the same CSI-RSports in accordance with an example embodiment. For inter-cluster Tier 2beams, all Tier 2 beams except the Tier 2 beams within the reportedinterference Tier 1 beams may reuse the same CSI-RS ports for sendingreference signals in accordance with one example. Thus, inter-clusterCSI-RS ports may be reused, which can greatly reduce the beamformedCSI-RS overhead with massive antennas in NR cellular systems, amongothers.

In another embodiment described in detail below, neighbor port reductionbased CSI-RS improves both KP-based and beamformed CSI-RS in a givencellular system. For example, an antenna port class can be defined withsize M as a group containing M neighbor antenna ports. In some cases,antenna port class formats with size M are defined as the methods of howthe M neighboring antennas form a class in a large two-dimensionalantenna array. With the same port class size, different port classformats are formed by partitioning different ports into port classes.

In an example, an eNB may select the port class size M and formatpattern index from at least some or up to all available port classformats, with the maximum size which guarantees the minimum acceptablequantization error among all UEs not to exceed a given threshold δ, forinstance a predetermined threshold. The selection may be based on thefull channel estimation, which can be obtained by the channelreciprocity feature (for TDD systems) or the legacy orthogonal CSI-RS(for FDD systems). For antenna elements in the same class, in anexample, only one CSI-RS port and the same REs per class are used tosend reference signals. The CSI-RS symbols transmitted on the antennaelements in one class may be precoded by a normalized vector with thesame weights on all antenna elements.

The port class format selection mechanism for a given eNB may be basedon received CSI reports from UEs, as described below. An eNB maycalculate the quantization error between the reported PMI and the fullchannel PMI obtained from SRS (TDD) or the legacy CSI-RS (FDD). If thequantization error is less than a given threshold, the eNB may keepusing the same port class format. Otherwise, it may select a port classformat with a smaller size.

Thus, neighbor antenna elements in the same class may be assigned withthe same CSI-RS port, which may greatly reduce the CSI-RS overhead by afactor of M with massive antennas in NR cellular systems. This iscompatible with KP-based CSI-RS scheme and beamformed based CSI-RSscheme as well as the legacy orthogonal CSI-RS scheme in LTE.

Referring now to FIGS. 32 and 33, an improved Beamformed CSI-RS with aCluster-Specific feature, in accordance with an example embodiment, isnow discussed. In an example, two tiers of 3D antenna beams are formed.For example, wide beams are referred to herein as Tier 1 beams andnarrow beams (as compared to the wide beams) are referred to herein asTier 2 beams. FIG. 32 shows an example of how a Tier 1 beam covers alarger service area as compared to Tier 2 beams. As shown, a Tier 1 beamcontains multiple small areas covered by Tier 2 beams.

Referring in particular to FIG. 33, an example system 3300 is shown thatincludes an eNB 3302 and plurality of mobile devices (e.g., UEs), whichcommunicate in a network. As shown, a UE1 and a UE 2 are in cluster 1(C1), and UE_(m) and UE_(m+1) are in cluster 2 (C2). It will beappreciated that the example system 3300 is simplified to facilitatedescription of the disclosed subject matter and is not intended to limitthe scope of this disclosure. Other devices, systems, and configurationsmay be used to implement the embodiments disclosed herein in additionto, or instead of, a system such as the system illustrated in FIG. 33,and all such embodiments are contemplated as within the scope of thepresent disclosure. For example, the illustrated eNB may be implementedalternatively by an eNB-like entity, an apparatus that is part of aradio access network, or the like.

Inter-cluster CSI-RS measurement is now described, which can be referredto as stage 1. At 4202, in accordance with the illustrated example, theeNB 3302 forms the Tier 1 beams based on the UEs' geographical locationinformation. The UEs may report their geographical location informationto the eNB 3302 periodically, such as from GPS, PRS, or WiFi basedmeasurement. It will be understood that other methods can also beapplied to obtain the location information. Tier 1 beams' accuracyrequirements may be satisfied by the available methods. In addition,other UE context information, such as, for example user type (static ormobile), velocity (x km/h), traffic/service type (e.g. videoconferencing, gaming/entertainment, web browsing), traffic/servicescheduling (e.g. day time traffic, night time), etc., may be piggybackedin the UL messages to help 3D fixed or dynamic beam formation at the eNB3302. At 4204, the eNB 3302 may conduct beamformed CSI-RS with Tier 1beams. Because the Tier 1 beams have a wider beamwidth as compared tothe Tier 2 beams for example, the Tier 1 beams can be referred to aswide beams, and the total number of Tier 1 beams to cover a cell isrelatively small, which reduces the overhead for CSI-RS ports. Forexample, based on the location information associated with each of theplurality of UEs, the eNB 3302 can form a wide beam, for instance afirst wide beam, that is sent to an area within a cell. Multiple Tier 1beams may be received by each of the UEs. Stated another way, each UEmay receive or detect a plurality of wide beams. At 4206, each UEcalculate the channel state information associated with each of thesebeams (the detected wide beams). Based on the channel state information,the UE may select an optimal Tier 1 (wide) beam from the plurality ofwide beams. The optimal wide beam may be the beam with the maximumchannel quality indication (CQI) as compared to the other detected Tier1 beams. As used herein, the terms wide beam and Tier 1 beam may be usedinterchangeably, without limitation. Similarly, as used herein, theterms narrow beam and Tier 2 beam may be used interchangeably, withoutlimitation.

At 4208, in accordance with the illustrated example, each of theplurality of UEs calculates Tier 1 Beam CSI feedback. For example, ifthere exists more than one Tier 1 beam with the maximum CQI for a givenUE, the UE may select one of those beams as the optimal Tier 1 beamusing a secondary metric. The secondary metric may include at least oneof, for example and without limitation, the maximum reference signalstrength/quality (e.g., Reference Signal Received Quality (RSRQ),Reference Signal Received Power (RSRP), or the maximum Received SignalStrength Indicator (RSSI)). In some cases, if there is still more thanone optimal Tier 1 beam after breaking the tie with the secondary beamevaluation metric, the UE may randomly select one of these beams as theoptimal Tier 1 beam. Under this case, the other beam(s) with the samemaximum CQI will be reported as interference Tier 1 beam(s) at 4208. At1108, the UE may then report the optimal Tier 1 beam index to the eNBwith related CQI, PMI, RI, etc. The number of digits needed to reportthis Tier 1 beam index field may be reduced as compared to the currentbeamformed CSI-RS scheme because the Tier 1 has a wider beamwidth andthe total number of Tier 1 beams to cover a cell is relatively small,which reduces the overhead for CSI feedback report for NR MIMO systems.

Still referring to FIG. 33, at 4212, in accordance with the illustratedexample, based on the received reports from the UEs, the eNB 3302 maygroup select UEs of the one or more mobile devices into a first cluster.For example, as shown, UE1 and U2 is grouped into a first cluster (C1),and UE_(m) and UE_(m+1) are grouped into a second cluster (C2). Based onthe reported optimal beam information from UEs, the eNB 3302 can defineUE clusters. In some cases, all the UEs that report the same optimalTier 1 beam are grouped into one cluster. Thus, in an example, each Tier1 beam covers only one UE cluster, and each cluster is associated withonly one Tier 1 beam. Thus, the eNB can send the first wide beam (WB I)to the first cluster. As shown in FIG. 32, in accordance with theillustrated example, one cluster may be covered by one Tier 1 beam. Inaccordance with the illustrated example, WB I covers the service area ofC1 and WB II covers the service area of C2. In addition, one cluster maybe covered by multiple Tier 2 beams. For example, as shown, narrow beams(NBs) 1, 2 and 3 cover the service area of C1 and NBs 4, 5 and 6 coverthe service area of C2.

At 4210, each UE may also identify one or more interference Tier 1beams. Thus, the eNB 3302 may receive an indication, from one or more ofthe mobile devices in the first cluster, of a second wide beam that isassociated with a second cluster of mobile devices. The indication mayidentify the second wide beam as an interference beam. For example, UEsmay identify interference beams based on the calculated channel stateinformation. In some cases, if a Tier 1 beam has a received power thatis greater than a predefined threshold, or if a Tier 1 beam has areceived power which is greater than the received power level of theoptimal Tier 1 beam minus a predefined threshold, or if a Tier 1 beamhas a received power lower than a predefined threshold or lower than thereceived power level of the optimal Tier 1 beam minus a predefinedthreshold but it has been detected as a Tier 1 beam with the samemaximum CQI as the optimal Tier 1 beam identified in the previous step,then the UE reports its one or more beam indices to the eNB.

The predefined threshold may be an absolute threshold or a thresholdthat is defined relative to the received power (e.g., RSRP) value of theoptimal Tier 1 beam at a given UE. In either case, the thresholds can beconfigured by eNB. The threshold may be UE-specific, beam-specific,cell-specific, or common to the UEs. The eNB may signal the thresholdvalue to the UE via common RRC signaling (e.g., system informationbroadcast) or dedicated signaling, for instance RRC dedicated signaling.In the latter example, a given UE may be allowed to use a thresholdvalue received while the UE was previously connected to the network. TheCQI, PMI and RI might not need to be reported with the interference Tier1 beam(s) in some cases. The interference Tier 1 beam information may beused by eNB to decide the inter-cluster interference in the stage 2process shown in FIG. 35. For example, as shown in FIG. 32, some UEs inthe edge of cluster 1 (C1) (overlapping with cluster 4 (C4)) may reportTier 1 WB I as the optimal beam and also report Tier 1 WB IV as theinterference Tier 1 beam to the eNB.

In an example, if the interference Tier 1 beam has a received powerwhich is lower than a predefined threshold or a received power which isa predefined threshold lower than the received power level of theoptimal Tier 1 beam, and it has not been detected to have the samemaximum signal strength/quality in the previous step, then there mightbe no need to report the CQI of the interference Tier 1 beam to the eNB3302. In this example, inter-cluster interference can be low andignored. For example, as shown in FIG. 34, UEs in C2 or C3 (nooverlapping with other clusters) might not report any interference Tier1 beam.

For inter-cluster beams, the same CSI-RS ports/REs for sending referencesignals for Tier 1 beams may be reused in the next period. In oneexample, if an interference Tier 1 beam is reported, which implies thatthere is high inter-cluster beam interference, the inter-cluster Tier 1beams cannot use the same CSI-RS ports (e.g., WB I and WB IV as shown inFIG. 34). For inter-cluster Tier 1 beams, in accordance with an exampleembodiment, all Tier 1 beams except the Tier 1 beams reported as theinterference Tier 1 beam may reuse the same CSI-RS ports for sendingreference signals (e.g., WBI and WB II as shown in FIG. 32). The Tier 1beams for CSI-RS measurements may be periodic with low frequency oraperiodic.

Still referring to FIG. 33, at 4214, per each cluster, in accordancewith the illustrated example, the eNB 3302 only needs to send beamformedCSI-RS for the Tier 2 beams within the assigned Tier 1 beam. Forexample, if cluster 1 is assigned to use Tier 1 beam WB I based on thestage 1 process, then eNB only needs to send Tier 2 beam NB1, NB2, andNB3 for cluster 1. This is referred to as intra-cluster CSI-RSmeasurement as compared to the inter-cluster CSI-RS measurementconducted in Stage 1, which is also referred to herein ascluster-specific CSI-RS.

In accordance with an example embodiment, all intra-cluster Tier 2 beamsuse different CSI-RS ports for sending reference signals, e.g., (NBs 1,2, 3), (NBs, 4, 5, 6) and (NBs 7, 8, 9) as shown in FIG. 32. Forinter-cluster Tier 2 beams, if interference Tier 1 beams are reported at4210, which implies that there is high inter-cluster beam interference,the corresponding inter-cluster Tier 2 beams, in particular thecorresponding inter-cluster Tier 2 beams of that interference Tier 1beams, cannot use the same CSI-RS ports. For example, NBs 1, 2, 3 andNBs, 10, 11 shown in FIG. 32 cannot use the same antenna ports as eachother. For inter-cluster Tier 2 beams, in accordance with an example,all Tier 2 beams except the Tier 2 beams within the reportedinterference Tier 1 beams from stage 1, can reuse the same CSI-RS portsfor sending reference signals, e.g. (NBs 1, 4, 7), (NBs 2, 5, 8) and(NBs 3, 6, 9) as shown in FIG. 32.

Thus, in accordance with an example, regardless of how many UE clustersare defined per cell and regardless of how many Tier 1 and 2 beams areformed per cell, the number of required CSI-RS ports are only tied tothe maximum number of Tier 2 beams within a cluster and to the reportedinterference beams, which less than the number of total beams. In somecases, the periodicity of the Tier 2 beam CSI-RS measurement (at 4216and 4218) may be more frequent than Tier 1 beam CSI-RS measurement instage 1.

By way of example, assume there are 8 antenna ports (assuming all in thehorizontal dimension) and 4 wider beams, the RB diagram in FIG. 34 showshow the Tier 1 beam and CSI-RS ports/REs can be allocated per RB withelevation beamforming. The CSI-RS can be reused with spatial separation.For example, WBs I, II and III use the same CSI-RS ports/REs, withoverlapping CSI-RS allocation.

In some cases, to efficiently enhance the current CSI-RS design toreduce the CSI-RS overhead, the illustrated stage 2 process can beconducted more frequently than that of the illustrated stage 1 process.Thus, inter-cluster Tier 2 beams (e.g., group 1: NB 1, NB 4, NB 7; group2: NB 2, NB 5, NB 8; group 3: NB 3, NB 6, NB 9) can reuse the same 8CSI-RS REs, which are shown as three overlapping instances in FIG. 35.As stated above, with respect to beamformed CSI-RS, each beam may useall 8 horizontal ports/REs with its weighting vector applied.Additionally, each group may use 8 REs with spatial reuse. The totalpower may be equally shared by the overlapping CSI-RS symbols per RE. Insome cases, the overlapping clusters do not reuse the same ports (e.g.,NB 10, NB 11 as shown in FIG. 35). It will be understood that otherallocation methods (e.g., the frequency division based CSI-RSallocation) may be utilized as desired and as appropriate.

Turning now to CSI-RS sequence design to generate cluster-specificCSI-RS sequences based on the existing sequence generation methodology,different random sequences can be generated per cluster to reduce theinterference among the reused inter-cluster CSI-RS Tier 2 beams at thereceiver, for example, when the RE carries CSI-RS symbols for more thanone Tier 2 beam as shown in FIG. 35. In accordance with an exampleembodiment, a cluster ID can be included in the sequence generation toensure that each cluster has its own CSI-RS sequence per cell. Then theequation (7) applies:

c _(init)=2¹⁰·(7·(n′ _(s)+1)+l+1)·(2·N _(ID) ^(CSI)+2N _(ID)^(Cluster)+1)+2·N _(ID) ^(CSI) +N _(CP)  (7)

where N_(ID) ^(Cluster) is the cluster identification per cell. Also, insome cases, the eNB needs to signal N_(ID) ^(Cluster) to the UEs, sothat each UE can generate the defined CSI-RS sequence. The signaling ofN_(ID) ^(Cluster) can be carried out in multiple ways, for example andwithout limitation:

-   -   It can be added to other DCI formats as a new field or a new        special DCI format can be created and sent from eNB to UE via        PDCCH or ePDCCH.    -   It can be added in any future NR downlink control channels        because NR cellular systems may have new designs of control        channels other than PDCCH and ePDCCH.

The new Cluster ID field proposed herein can be in a new or reused DCIformat, as illustrated herein. The information can be periodically oraperiodically transmitted via PDCCH or ePDCCH or any future NR controlchannels based on, for example, a given UE's location, speed, or othercontext information. With static or very-low-mobility scenario, it canbe less frequently transmitted as compared to a high mobility scenario.

TABLE 11 Example of Cluster ID field in an example DCI Format Field NameLength (Bits) Cluster ID 5 MCS 5 PMI confirmation for precoding 1 . . .. . .

As described above, in some cases, no matter how many UE clusters aredefined per cell and no matter how many Tier 1 and Tier 2 beams areformed per cell, the number of REs used for transmitting CSI-RS will notincrease with the increasing number of antenna beams. The number of REsmight only be related to the number of Tier 2 beams per cluster (spatialseparation) and the reported interference beams, which might only affectthe number of overlapping port instances per RE. Thus, the CSI-RSoverhead can be greatly reduced by the proposed two-stage procedure andthe inter-cluster port reuse mechanisms described above.

In an example embodiment in which Tier 1 and Tier 2 beams are formed,the Tier 1 beams may be used for downlink coverage in the cell, forexample, to support full initial access to the NR downlink commonchannels, such as synchronization, broadcasting, or the like. The Tier 1beams may also be used to support the uplink reception coverage in thecell for NR uplink initial accessing channels, such as, for example, therandom accessing channel, non-orthogonal grant-less accessing channel,etc. The Tier 2 beams may be used for UE-specific downlink datatransmissions, such as, for example, NR downlink control and datachannels for improving the system capacity.

Turning now to an improved KP-Based CSI-RS and Beamformed CSI-RS withNeighbor Port Reduction Feature, as described below, the KP-based CSI-RSand beamformed CSI-RS schemes in a large antenna array can reduce CSI-RSoverhead.

By way of example, an antenna port class with size M is defined as agroup containing M neighbor antenna ports. A port class format with sizeM is a particular way in which every M neighbor antenna ports form anantenna port class. The port class format with size M=1 is equivalent tothe original antenna port format without any reduction. With size M>1,the CSI-RS port will be reduced by a factor of M. With the same classsize, it may have different patterns to form the class with differentneighbors.

The port class formats can be pre-defined, and the eNB and UEs can sharethe knowledge of the available port class formats. The eNB candynamically select the port class format based on the UEs' feedback andthe calculated quantization error at the eNB.

An exemplary port class format with M=2 for a 16×16 antenna array withKP-based CSI-RS scheme is shown in FIG. 36. As stated, the eKP-basedCSI-RS ports are assigned to the antennas in the first column and thefirst row. Referring to FIG. 36, the neighbor antennas in the same classwith size M=2 are indicated by a common letter reference (e.g., A, B, C,etc.). FIG. 37 shows an example port class format with M=2 for a 16×16antenna array with beamformed CSI-RS scheme. As shown, one beamformedCSI-RS port is assigned to each column and the reference signals on eachcolumn are precoded by the same weighting vector. Referring to FIG. 37,the antenna ports in the same class are indicated by the same letterreference (e.g., A, B, C, etc.).

Referring also to FIG. 38, an example system 3800 is shown that includesan eNB 3802 and a plurality of mobile devices (e.g., UEs), whichcommunicate in a network. As shown, a UE1, a UE2, a UE_(m), and aUE_(m−1) represent the plurality of UEs. It will be appreciated that theexample system 3800 is simplified to facilitate description of thedisclosed subject matter and is not intended to limit the scope of thisdisclosure. Other devices, systems, and configurations may be used toimplement the embodiments disclosed herein in addition to, or insteadof, a system such as the system illustrated in FIG. 38, and all suchembodiments are contemplated as within the scope of the presentdisclosure. For example, the illustrated eNB may be implementedalternatively by an eNB-like entity, an apparatus that is part of aradio access network, or the like.

In accordance with the illustrated embodiment, at 1602, to select theCSI-RS port class format, the eNB obtains the full channel estimation.This can be performed periodically with a long duration oraperiodically. For a TDD system, the eNB may take advantage of fullchannel reciprocity feature to use the UL channel CSI obtained from ULSRS for DL channel estimation. For a FDD system, the eNB may send CSI-RSthrough all ports as the legacy orthogonal CSI-RS, and UE will feedbackCSI report according to the full channel information.

At 1604, in accordance with the illustrated example, based on theobtained CSI of the ports, the eNB selects a port class format from theavailable port class formats, with the maximum size which guaranteesthat the minimum acceptable quantization error among all the UEs willnot exceed a given threshold δ. The quantization error may be calculatedbased on the difference between the full channel PMI and the reducedPMI.

For antenna elements in the same class, in accordance with an example,only one CSI-RS port and the same RE is used to send reference signals.The CSI-RS symbols transmitted on the antenna elements in one class canbe precoded by a normalized vector with the same weights on all antennaelements.

At 1606, in accordance with the illustrated example, the eNB 3802 thensignals the information of the selected port class format (e.g., portclass size M and format pattern index with size M) to UEs. The signalingcan be done via downlink control channels or other methods as desired(e.g., Radio Resource Control (RRC) signaling, MAC Control Element (CE),which might be more dynamic than RRC level signaling). For example, thedownlink control channel can be a new or reused DCI format carried onPDCCH or ePDCCH, or any downlink control channels in a NR system. Insome cases, when size M=1, it indicates the normal CSI-RS port, and whensize M>1, it indicates the reduced CSI-RS port.

At 1608, each UE can obtain port class size M and a format pattern indexwith size M. At 1610, in accordance with the illustrated example, eachUE can send feedback, in a CSI report for example, according to thereduced channel, such as CQI and/or PMI and RI for example. In somecases, depending on the port class size M, the PMI can be calculatedbased on different codebooks. The report at 1610 may reduce the CSIfeedback overhead for MIMO systems, for instance NR MIMO systems. Forexample, the number of digits needed for CSI report according to thereduced channel will be less than the ones for the current KP-based orbeamformed CSI-RS scheme, since with less CSI-RS ports, the codebooksize for PMI calculation is reduced, and as a result, the number of bitsin the PMI report is also reduced. At 1612, after the NB obtains CSIreports from UEs, the eNB can calculate the quantization error betweenthe reported PMI and the full channel PMI learned from 1602. If themaximum error among the UEs is less than the given error threshold δ,the eNB 3802 may use the same port class format, and thus maintain theport size M. If the maximum error among the UEs is greater than thegiven error threshold δ, the eNB may select a port class format with asmaller size (e.g., M−1) at 1614. The above described steps may berepeated, as shown by 1616 and 1618.

FIG. 39 depicts an example port class format selection procedure thatcan be performed at the eNB 3802 or an access node. For example, at3902, the node receives one or more CSI reports from UEs. At 3904, thenode may calculate a maximum quantization error, with a port classformat of size M and a pattern index I among the UEs. At 3908, the nodedetermines whether the error is less than a threshold. If the error isless than the threshold, the process proceeds to 3910, where a CSI-RSwith a port class of size M and pattern index I is selected. If theerror is greater than the threshold, the process proceeds to 3906, wherethe node selects a format index to minimize the maximum quantizationerror with port class formats of size M among the UEs. After 3906, theprocess may return to 3908, where error is compared to the threshold.

By way of example, assume there is a 16×16 antenna array and theKP-based CSI-RS is applied. The RB diagram in FIG. 38 shows an exampleof how the CSI-RS ports/REs are allocated per RB to estimate the fullchannel without port reduction, which requires 32 REs for KP-basedCSI-RS. By way of further example, suppose that the port class formatwith size 2 in FIG. 36 is selected by the eNB. To efficiently enhancethe current CSI-RS design to reduce the CSI-RS overhead in accordancewith an example embodiment, the antennas in the same class can use thesame CSI-RS REs, which reduces the number of required REs from 32 to 16as shown in FIG. 43.

By way of yet another example, assume there is a 16×16 antenna array andthe beamformed CSI-RS is applied. The RB diagram in FIG. 42 shows anexample of how the CSI-RS ports/REs can be allocated per RB forbeamformed CSI-RS to estimate the full channel, which requires 16 REswithout port reduction. Assuming that the port class format with size 2in FIG. 37 is selected by the eNB, to efficiently enhance the currentCSI-RS design to reduce the CSI-RS overhead in accordance with theexample embodiment, the antennas in the same class can use the sameCSI-RS REs, which reduces the number of required REs from 16 to 8 asshown in FIG. 43.

To support the above-described neighbor port reduction, port class sizeand format pattern index is sent from the eNB to the UEs, and each UEdetermines the codebook for the PMI calculation based on them. It willbe understood that these parameters can be carried in multiple messagesas desired. For example, the parameters can be added to other DCIformats as new fields or a new special DCI format can be created that issent from the eNB to each UE via PDCCH or ePDCCH. Further, theseparameters can be added in future NR downlink control channels becauseit is recognized herein that future cellular systems may have controlchannels other than PDCCH and ePDCCH. The proposed port class size andformat pattern index fields in a new or reused DCI format areillustrated in Table 12 by way of example. The information can beperiodically or aperiodically transmitted via PDCCH or ePDCCH or anyfuture NR control channels based on, for example, a given UE's location,speed, or other context information associated with the UE. When appliedto a static or low-mobility scenario, it can be less frequentlytransmitted as compared to a high-mobility scenario, in accordance withone example.

TABLE 12 Example of Port Class Size field and Format patter index fieldin a DCI Format Field Name Length (Bits) Port Class Size 3 FormatPattern Index 3 MCS 5 PMI confirmation for precoding 1 . . . . . .

As described above, regardless of whether the KP-based CSI-RS scheme orthe beamformed CSI-RS scheme is applied, the number of REs used fortransmitting CSI-RS may be further reduced by a factor of M. It will beunderstood that the embodiments described herein can also be applied toother CSI-RS schemes, such as the legacy orthogonal CSI-RS scheme forexample.

Turning now to DL reference signals, to support a wide range of usermobility scenarios with low-latency in NR, reference signaling may beenhanced in DL NR.

In accordance with various example embodiments, DM-RS location within aslot/mini-slot or subframe may be flexible and adaptive toscenario-specific performance requirements. As an example case, a givenDM-RS may be front-loaded, so that the proximity of DM-RS to controldata allows accurate estimation channel at control data resources,thereby rendering accurate demodulation/decoding of control data.Further, an early DM-RS may minimize the delay in demodulation/decodingby delivering channel estimates early on.

FIG. 44 shows support for two ports via OCC. In general, support forN-layers can be achieved via appropriate codes. FIG. 45 shows that aDM-RS may be placed in the middle of a transmission interval so thatchannel estimates obtained over the entire duration of the interval maybe more accurate as compared to having front-loaded DM-RS. Although thelatency is higher for decoding control information, in some cases, mMTCand eMBB may be able to tolerate the latency.

FIG. 46 shows an example DM-RS allocated with higher density in thetransmission interval. For example, for high Doppler scenarios, theDM-RS may be allocated in multiple symbols spread over time, to enableaccurate channel estimation.

For a scenario in which the UEs have low mobility, the DM-RS may beplaced at the end of a minislot ‘i”, and be used to provide channelestimates to subframes ‘i’ and ‘i+1’. Similarly, a given DM-RS can beshared between multiple UEs. For UEs 1 and 2 that have consecutive RBsin the same band, the DM-RS may be placed at the end of subframe ‘1’,and may be used to provide channel estimates to two subframes belongingto different users. FIGS. 47A and 47B depict the aforementionedscenarios. In particular, FIG. 47A depicts sharing between two subframesof the same user, and FIG. 47B depicts sharing between subframes of twodifferent users who are precoded the same way.

NR can support PRB bundling and can allow flexible location of DM-RSresources in the bundled PRBs. In FIG. 48, two bundled PRBs withdifferent DM-RS patterns undergo the same precoding. PRB1 may have theDM-RS allocated in a manner in which it can be shared with a neighboringUE. As shown, PRB2 may have a lower density of DM-RS allocation ascompared to PRB1.

In some cases, the resource assignment of DM-RS can be either dynamic orsemi-static. Dynamic signaling can be done through DCI. A list ofpossible DM-RS patterns (locations and sequences) may be predetermined,out of which one may be assigned to a given UE. The assigned resourcemay be indicated through an index into the list. When semi-staticsignaling is used, for example, RRC or MAC CE updates may indicate theDM-RS configurations. The DM-RS may have the same numerology as data.

Turning now to Tracking Reference Signals (TRS) for phase tracking inNR, it is recognized herein that phase noise increases with increasingcarrier frequency. Phase tracking issues in NR are now addressed.

In some cases, a TRS is not sent all the time. For example, a trackingRS might only be sent when needed, thereby avoiding costly transmissionoverhead brought by TRS transmissions. One or more of the followingfactors may influence the choice of switching TRS on or off, presentedby way of example and without limitation:

-   -   Modulation order: The absence of phase tracking RS may have a        more deteriorating effect on BLER when data is higher order        modulated as compared to when it is lower order modulated.    -   Carrier frequency: In some cases, increasing carrier frequency        may necessitate turning on Tracking RS.    -   UE speed: In some cases, increasing UE speed increases the        Doppler, which implies the need to turn on Tracking RS.    -   Sub-carrier Spacing: In some cases, increased sub-carrier        spacing may increase inherent immunity of system to carrier        frequency offset, thereby reducing the need for Tracking RS.

A given TRS may be UE-specific or cell-specific. On/Off signaling fortracking RS may be done via distinct signaling, for example, dependingon whether it is UE-specific or cell-specific. In an example in whichTRS is UE-specific, it may be configured via RRC signaling and turnedon/off through RRC signaling/MAC CE updates, or dynamically through theDCI. In an example in which a given TRS is cell/beam wide, systeminformation may be used to signal its presence and resources.

FIG. 49 shows an example cell/beam wide case in which TRS resources areassigned in specific locations in the grid. Enough TRS resources may bereserved so that UEs that may operate only in certain subbands ofavailable spectrum can access the TRS. FIGS. 50A-C show an exampleUE-specific case in which each UE can have TRS resources assignedaccording to its SNR, modulation, numerology, etc.

With respect to an example UE-specific TRS, a tracking RS may beprecoded. Further, location and sequence of Tracking RS may depend onone or more of beam ID, cell ID, or UE-specific resource such as, forexample, a root/shift of a sequence assigned to the UE or a location ofthe DL resources for the UE.

In an example cell/beam wide TRS, the TRS may be transmitted inresources that are known to the UEs. Further, the TRS may be a functionof one or more of a Cell ID or a Beam ID.

In an example, a TRS transmission may be configured on one or moreports. In some scenarios it may be sufficient to track phase bytransmitting the TRS on a single port. So, in an example, the TRS on asingle port is supported by default. A NR system may also support moreports for TRS. The resources for the ports may be configured for bothcell/beam wide and UE specific use cases through DCI or RRC signaling.

Turning now to SRS resource allocation, in an example, NR-SRS numerologyand resources are allocated in a manner compatible with supported dataand control signal numerologies, and TDM/FDM multiplexing of multipleusers. Example embodiments now described can address NR-SRS signalingaspects when multiple numerologies are supported simultaneously in acarrier. In an example, an NR-Node can allocate various resources forNR-SRS transmission. For example, the NR node can allocate certain OFDMsymbols, or portions of the OFDM symbols may be reserved in a cell-wideor beam-wide manner for transmitting SRS in each supported numerology.As shown in FIG. 51, the network divides the transmission BW into twonumerologies: Numerology 1 that supports 15 KHz subcarrier spacing; andNumerology 2 that supports 60 KHz subcarrier spacing. Within thebandwidth assigned to each numerology, the SRS transmission may have thesame numerology.

The NR node can allocate certain OFDM symbols, or portions of the OFDMsymbols may be reserved in a cell-wide or beam-wide manner in areference numerology that may be associated to the carrier frequency orindicated by the system information. This aspect is illustrated by wayof example in FIG. 52, where the SRS is always transmitted at a fixednumerology, although other signaling may occur in other numerologies.FIG. 52 shows an example in which an SRS is transmitted over 1 symbolcorresponding to Numerology 1. The specific numerology can be assignedvia a semi-static configuration, such as RRC signaling for example, ordynamically assigned by the DL DCI, for example.

Alternatively, the SRS resources may be defined in units of time and maybe configured to support any numerology. In this example, the reservedtime may carry different numbers of NR-SRS symbols for differentnumerologies. This aspect is illustrated in FIG. 54 by way of example,where the NR-SRS resource is reserved for a fixed time duration T.Different numerologies may be used within this duration. For example, 1symbol of NR-SRS may be reserved at 15 KHz subcarrier spacing(Numerology 1), or 2 symbols of NR-SRS may be reserved at 60 KHzsubcarrier spacing (Numerology 2).

User equipment (UE) can be any device used by an end-user tocommunicate. It can be a hand-held telephone, a laptop computer equippedwith a mobile broadband adapter, or any other device. For example, theUE can be implemented as the wireless transmit/receive units (WTRUs) 102(such as 102 a, 102 b, 102 c, and/or 102 d) of FIG. 53A-F.

Radio Access nodes can include Node B, eNode B, 5G RAN nodes or anyother node to provide access, which could be either located in thecontrol plane, or in the user plane, and could be located in acentralized location (e.g., data center, cloud, i.e. central controlleror central unit in support of virtualization) or could be located at theedge of the RAN as a distributed RAN unit for e.g. a Transmit ReceptionPoint (TRP) with RAN functions located at the edge of the RAN. Radioaccess nodes (radio access nodes 103/1004/105) can be implemented as oneof the apparatus of FIGS. 53A-F.

Similarly, core/control nodes can include MME, 5G CN control node, 5Gnetwork control entity, control unit located in the control plane, S-GW,P-GW or 5G core network equivalent node, 5G core network gateway or userdata processing unit located in the data plane or user plane.Core/control nodes (core network 106/107/109) can be implemented as oneof the apparatus of FIGS. 53A-F.

The 3rd Generation Partnership Project (3GPP) develops technicalstandards for cellular telecommunications network technologies,including radio access, the core transport network, and servicecapabilities—including work on codecs, security, and quality of service.Recent radio access technology (RAT) standards include WCDMA (commonlyreferred as 3G), LTE (commonly referred as 4G), and LTE-Advancedstandards. 3GPP has begun working on the standardization of nextgeneration cellular technology, called New Radio (NR), which is alsoreferred to as “5G”. 3GPP NR standards development is expected toinclude the definition of next generation radio access technology (newRAT), which is expected to include the provision of new flexible radioaccess below 6 GHz, and the provision of new ultra-mobile broadbandradio access above 6 GHz. The flexible radio access is expected toconsist of a new, non-backwards compatible radio access in new spectrumbelow 6 GHz, and it is expected to include different operating modesthat can be multiplexed together in the same spectrum to address a broadset of 3GPP NR use cases with diverging requirements. The ultra-mobilebroadband is expected to include cmWave and mmWave spectrum that willprovide the opportunity for ultra-mobile broadband access for, e.g.,indoor applications and hotspots. In particular, the ultra-mobilebroadband is expected to share a common design framework with theflexible radio access below 6 GHz, with cmWave and mmWave specificdesign optimizations.

3GPP has identified a variety of use cases that NR is expected tosupport, resulting in a wide variety of user experience requirements fordata rate, latency, and mobility. The use cases include the followinggeneral categories: enhanced mobile broadband (e.g., broadband access indense areas, indoor ultra-high broadband access, broadband access in acrowd, 50+ Mbps everywhere, ultra-low cost broadband access, mobilebroadband in vehicles), critical communications, massive machine typecommunications, network operation (e.g., network slicing, routing,migration and interworking, energy savings), and enhancedvehicle-to-everything (eV2X) communications. Specific service andapplications in these categories include, e.g., monitoring and sensornetworks, device remote controlling, bi-directional remote controlling,personal cloud computing, video streaming, wireless cloud-based office,first responder connectivity, automotive ecall, disaster alerts,real-time gaming, multi-person video calls, autonomous driving,augmented reality, tactile internet, and virtual reality to name a few.All of these use cases and others are contemplated herein.

FIG. 53A illustrates one embodiment of an example communications system100 in which the methods and apparatuses described and claimed hereinmay be embodied. As shown, the example communications system 100 mayinclude wireless transmit/receive units (WTRUs) 102 a, 102 b, 102 c,and/or 102 d (which generally or collectively may be referred to as WTRU102), a radio access network (RAN) 103/104/105/103 b/104 b/105 b, a corenetwork 106/107/109, a public switched telephone network (PSTN) 108, theInternet 110, and other networks 112, though it will be appreciated thatthe disclosed embodiments contemplate any number of WTRUs, basestations, networks, and/or network elements. Each of the WTRUs 102 a,102 b, 102 c, 102 d, 102 e may be any type of apparatus or deviceconfigured to operate and/or communicate in a wireless environment.Although each WTRU 102 a, 102 b, 102 c, 102 d, 102 e is depicted inFIGS. 53A-E as a hand-held wireless communications apparatus, it isunderstood that with the wide variety of use cases contemplated for 5Gwireless communications, each WTRU may comprise or be embodied in anytype of apparatus or device configured to transmit and/or receivewireless signals, including, by way of example only, user equipment(UE), a mobile station, a fixed or mobile subscriber unit, a pager, acellular telephone, a personal digital assistant (PDA), a smartphone, alaptop, a tablet, a netbook, a notebook computer, a personal computer, awireless sensor, consumer electronics, a wearable device such as a smartwatch or smart clothing, a medical or eHealth device, a robot,industrial equipment, a drone, a vehicle such as a car, truck, train, orairplane, and the like.

The communications system 100 may also include a base station 114 a anda base station 114 b. Base stations 114 a may be any type of deviceconfigured to wirelessly interface with at least one of the WTRUs 102 a,102 b, 102 c to facilitate access to one or more communication networks,such as the core network 106/107/109, the Internet 110, and/or the othernetworks 112. Base stations 114 b may be any type of device configuredto wiredly and/or wirelessly interface with at least one of the RRHs(Remote Radio Heads) 118 a, 118 b and/or TRPs (Transmission andReception Points) 119 a, 119 b to facilitate access to one or morecommunication networks, such as the core network 106/107/109, theInternet 110, and/or the other networks 112. RRHs 118 a, 118 b may beany type of device configured to wirelessly interface with at least oneof the WTRU 102 c, to facilitate access to one or more communicationnetworks, such as the core network 106/107/109, the Internet 110, and/orthe other networks 112. TRPs 119 a, 119 b may be any type of deviceconfigured to wirelessly interface with at least one of the WTRU 102 d,to facilitate access to one or more communication networks, such as thecore network 106/107/109, the Internet 110, and/or the other networks112. By way of example, the base stations 114 a, 114 b may be a basetransceiver station (BTS), a Node-B, an eNode B, a Home Node B, a HomeeNode B, a site controller, an access point (AP), a wireless router, andthe like. While the base stations 114 a, 114 b are each depicted as asingle element, it will be appreciated that the base stations 114 a, 114b may include any number of interconnected base stations and/or networkelements.

The base station 114 a may be part of the RAN 103/104/105, which mayalso include other base stations and/or network elements (not shown),such as a base station controller (BSC), a radio network controller(RNC), relay nodes, etc. The base station 114 b may be part of the RAN103 b/104 b/105 b, which may also include other base stations and/ornetwork elements (not shown), such as a base station controller (BSC), aradio network controller (RNC), relay nodes, etc. The base station 114 amay be configured to transmit and/or receive wireless signals within aparticular geographic region, which may be referred to as a cell (notshown). The base station 114 b may be configured to transmit and/orreceive wired and/or wireless signals within a particular geographicregion, which may be referred to as a cell (not shown). The cell mayfurther be divided into cell sectors. For example, the cell associatedwith the base station 114 a may be divided into three sectors. Thus, inan embodiment, the base station 114 a may include three transceivers,e.g., one for each sector of the cell. In an embodiment, the basestation 114 a may employ multiple-input multiple output (MIMO)technology and, therefore, may utilize multiple transceivers for eachsector of the cell.

The base stations 114 a may communicate with one or more of the WTRUs102 a, 102 b, 102 c over an air interface 115/116/117, which may be anysuitable wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, cmWave,mmWave, etc.). The air interface 115/116/117 may be established usingany suitable radio access technology (RAT).

The base stations 114 b may communicate with one or more of the RRHs 118a, 118 b and/or TRPs 119 a, 119 b over a wired or air interface 115b/116 b/117 b, which may be any suitable wired (e.g., cable, opticalfiber, etc.) or wireless communication link (e.g., radio frequency (RF),microwave, infrared (IR), ultraviolet (UV), visible light, cmWave,mmWave, etc.). The air interface 115 b/116 b/117 b may be establishedusing any suitable radio access technology (RAT).

The RRHs 118 a, 118 b and/or TRPs 119 a, 119 b may communicate with oneor more of the WTRUs 102 c, 102 d over an air interface 115 c/116 c/117c, which may be any suitable wireless communication link (e.g., radiofrequency (RF), microwave, infrared (IR), ultraviolet (UV), visiblelight, cmWave, mmWave, etc.). The air interface 115 c/116 c/117 c may beestablished using any suitable radio access technology (RAT).

More specifically, as noted above, the communications system 100 may bea multiple access system and may employ one or more channel accessschemes, such as CDMA, TDMA, FDMA, OFDMA, SC-FDMA, and the like. Forexample, the base station 114 a in the RAN 103/104/105 and the WTRUs 102a, 102 b, 102 c, or RRHs 118 a, 118 b and TRPs 119 a, 119 b in the RAN103 b/104 b/105 b and the WTRUs 102 c, 102 d, may implement a radiotechnology such as Universal Mobile Telecommunications System (UMTS)Terrestrial Radio Access (UTRA), which may establish the air interface115/116/117 or 115 c/116 c/117 c respectively using wideband CDMA(WCDMA). WCDMA may include communication protocols such as High-SpeedPacket Access (HSPA) and/or Evolved HSPA (HSPA+). HSPA may includeHigh-Speed Downlink Packet Access (HSDPA) and/or High-Speed UplinkPacket Access (HSUPA).

In an embodiment, the base station 114 a and the WTRUs 102 a, 102 b, 102c, or RRHs 118 a, 118 b and TRPs 119 a, 119 b in the RAN 103 b/104 b/105b and the WTRUs 102 c, 102 d, may implement a radio technology such asEvolved UMTS Terrestrial Radio Access (E-UTRA), which may establish theair interface 115/116/117 or 115 c/116 c/117 c respectively using LongTerm Evolution (LTE) and/or LTE-Advanced (LTE-A). In the future, the airinterface 115/116/117 may implement 3GPP NR technology.

In an embodiment, the base station 114 a in the RAN 103/104/105 and theWTRUs 102 a, 102 b, 102 c, or RRHs 118 a, 118 b and TRPs 119 a, 119 b inthe RAN 103 b/104 b/105 b and the WTRUs 102 c, 102 d, may implementradio technologies such as IEEE 802.16 (e.g., Worldwide Interoperabilityfor Microwave Access (WiMAX)), CDMA2000, CDMA2000 1×, CDMA2000 EV-DO,Interim Standard 2000 (IS-2000), Interim Standard 95 (IS-95), InterimStandard 856 (IS-856), Global System for Mobile communications (GSM),Enhanced Data rates for GSM Evolution (EDGE), GSM EDGE (GERAN), and thelike.

The base station 114 c in FIG. 53A may be a wireless router, Home NodeB, Home eNode B, or access point, for example, and may utilize anysuitable RAT for facilitating wireless connectivity in a localized area,such as a place of business, a home, a vehicle, a campus, and the like.In an embodiment, the base station 114 c and the WTRUs 102 e, mayimplement a radio technology such as IEEE 802.11 to establish a wirelesslocal area network (WLAN). In an embodiment, the base station 114 c andthe WTRUs 102 d, may implement a radio technology such as IEEE 802.15 toestablish a wireless personal area network (WPAN). In yet anotherembodiment, the base station 114 c and the WTRUs 102 e, may utilize acellular-based RAT (e.g., WCDMA, CDMA2000, GSM, LTE, LTE-A, etc.) toestablish a picocell or femtocell. As shown in FIG. 53A, the basestation 114 b may have a direct connection to the Internet 110. Thus,the base station 114 c may not be required to access the Internet 110via the core network 106/107/109.

The RAN 103/104/105 and/or RAN 103 b/104 b/105 b may be in communicationwith the core network 106/107/109, which may be any type of networkconfigured to provide voice, data, applications, and/or voice overinternet protocol (VoIP) services to one or more of the WTRUs 102 a, 102b, 102 c, 102 d. For example, the core network 106/107/109 may providecall control, billing services, mobile location-based services, pre-paidcalling, Internet connectivity, video distribution, etc., and/or performhigh-level security functions, such as user authentication.

Although not shown in FIG. 53A, it will be appreciated that the RAN103/104/105 and/or RAN 103 b/104 b/105 b and/or the core network106/107/109 may be in direct or indirect communication with other RANsthat employ the same RAT as the RAN 103/104/105 and/or RAN 103 b/104b/105 b or a different RAT. For example, in addition to being connectedto the RAN 103/104/105 and/or RAN 103 b/104 b/105 b, which may beutilizing an E-UTRA radio technology, the core network 106/107/109 mayalso be in communication with another RAN (not shown) employing a GSMradio technology.

The core network 106/107/109 may also serve as a gateway for the WTRUs102 a, 102 b, 102 c, 102 d, 102 e to access the PSTN 108, the Internet110, and/or other networks 112. The PSTN 108 may includecircuit-switched telephone networks that provide plain old telephoneservice (POTS). The Internet 110 may include a global system ofinterconnected computer networks and devices that use commoncommunication protocols, such as the transmission control protocol(TCP), user datagram protocol (UDP) and the internet protocol (IP) inthe TCP/IP internet protocol suite. The networks 112 may include wiredor wireless communications networks owned and/or operated by otherservice providers. For example, the networks 112 may include anothercore network connected to one or more RANs, which may employ the sameRAT as the RAN 103/104/105 and/or RAN 103 b/104 b/105 b or a differentRAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, e.g., theWTRUs 102 a, 102 b, 102 c, 102 d, and 102 e may include multipletransceivers for communicating with different wireless networks overdifferent wireless links. For example, the WTRU 102 e shown in FIG. 53Amay be configured to communicate with the base station 114 a, which mayemploy a cellular-based radio technology, and with the base station 114c, which may employ an IEEE 802 radio technology.

FIG. 53B is a block diagram of an example apparatus or device configuredfor wireless communications in accordance with the embodimentsillustrated herein, such as for example, a WTRU 102. As shown in FIG.53B, the example WTRU 102 may include a processor 118, a transceiver120, a transmit/receive element 122, a speaker/microphone 124, a keypad126, a display/touchpad/indicators 128, non-removable memory 130,removable memory 132, a power source 134, a global positioning system(GPS) chipset 136, and other peripherals 138. It will be appreciatedthat the WTRU 102 may include any sub-combination of the foregoingelements while remaining consistent with an embodiment. Also,embodiments contemplate that the base stations 114 a and 114 b, and/orthe nodes that base stations 114 a and 114 b may represent, such as butnot limited to, transceiver station (BTS), a Node-B, a site controller,an access point (AP), a home node-B, an evolved home node-B (eNodeB), ahome evolved node-B (HeNB), a home evolved node-B gateway, and proxynodes, among others, may include some or all of the elements depicted inFIG. 53B and described herein.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 53Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 115/116/117. For example, in an embodiment,the transmit/receive element 122 may be an antenna configured totransmit and/or receive RF signals. Although not shown in FIG. 53A, itwill be appreciated that the RAN 103/104/105 and/or the core network106/107/109 may be in direct or indirect communication with other RANsthat employ the same RAT as the RAN 103/104/105 or a different RAT. Forexample, in addition to being connected to the RAN 103/104/105, whichmay be utilizing an E-UTRA radio technology, the core network106/107/109 may also be in communication with another RAN (not shown)employing a GSM radio technology.

The core network 106/107/109 may also serve as a gateway for the WTRUs102 a, 102 b, 102 c, 102 d to access the PSTN 108, the Internet 110,and/or other networks 112. The PSTN 108 may include circuit-switchedtelephone networks that provide plain old telephone service (POTS). TheInternet 110 may include a global system of interconnected computernetworks and devices that use common communication protocols, such asthe transmission control protocol (TCP), user datagram protocol (UDP)and the internet protocol (IP) in the TCP/IP internet protocol suite.The networks 112 may include wired or wireless communications networksowned and/or operated by other service providers. For example, thenetworks 112 may include another core network connected to one or moreRANs, which may employ the same RAT as the RAN 103/104/105 or adifferent RAT.

Some or all of the WTRUs 102 a, 102 b, 102 c, 102 d in thecommunications system 100 may include multi-mode capabilities, e.g., theWTRUs 102 a, 102 b, 102 c, and 102 d may include multiple transceiversfor communicating with different wireless networks over differentwireless links. For example, the WTRU 102 c shown in FIG. 53A may beconfigured to communicate with the base station 114 a, which may employa cellular-based radio technology, and with the base station 114 b,which may employ an IEEE 802 radio technology.

FIG. 53B is a block diagram of an example apparatus or device configuredfor wireless communications in accordance with the embodimentsillustrated herein, such as for example, a WTRU 102. As shown in FIG.53B, the example WTRU 102 may include a processor 118, a transceiver120, a transmit/receive element 122, a speaker/microphone 124, a keypad126, a display/touchpad/indicators 128, non-removable memory 130,removable memory 132, a power source 134, a global positioning system(GPS) chipset 136, and other peripherals 138. It will be appreciatedthat the WTRU 102 may include any sub-combination of the foregoingelements while remaining consistent with an embodiment. Also,embodiments contemplate that the base stations 114 a and 114 b, and/orthe nodes that base stations 114 a and 114 b may represent, such as butnot limited to transceiver station (BTS), a Node-B, a site controller,an access point (AP), a home node-B, an evolved home node-B (eNodeB), ahome evolved node-B (HeNB), a home evolved node-B gateway, and proxynodes, among others, may include some or all of the elements depicted inFIG. 53B and described herein.

The processor 118 may be a general purpose processor, a special purposeprocessor, a conventional processor, a digital signal processor (DSP), aplurality of microprocessors, one or more microprocessors in associationwith a DSP core, a controller, a microcontroller, Application SpecificIntegrated Circuits (ASICs), Field Programmable Gate Array (FPGAs)circuits, any other type of integrated circuit (IC), a state machine,and the like. The processor 118 may perform signal coding, dataprocessing, power control, input/output processing, and/or any otherfunctionality that enables the WTRU 102 to operate in a wirelessenvironment. The processor 118 may be coupled to the transceiver 120,which may be coupled to the transmit/receive element 122. While FIG. 53Bdepicts the processor 118 and the transceiver 120 as separatecomponents, it will be appreciated that the processor 118 and thetransceiver 120 may be integrated together in an electronic package orchip.

The transmit/receive element 122 may be configured to transmit signalsto, or receive signals from, a base station (e.g., the base station 114a) over the air interface 115/116/117. For example, in an embodiment,the transmit/receive element 122 may be an antenna configured totransmit and/or receive RF signals. In an embodiment, thetransmit/receive element 122 may be an emitter/detector configured totransmit and/or receive IR, UV, or visible light signals, for example.In yet an embodiment, the transmit/receive element 122 may be configuredto transmit and receive both RF and light signals. It will beappreciated that the transmit/receive element 122 may be configured totransmit and/or receive any combination of wireless signals.

In addition, although the transmit/receive element 122 is depicted inFIG. 53B as a single element, the WTRU 102 may include any number oftransmit/receive elements 122. More specifically, the WTRU 102 mayemploy MIMO technology. Thus, in an embodiment, the WTRU 102 may includetwo or more transmit/receive elements 122 (e.g., multiple antennas) fortransmitting and receiving wireless signals over the air interface115/116/117.

The transceiver 120 may be configured to modulate the signals that areto be transmitted by the transmit/receive element 122 and to demodulatethe signals that are received by the transmit/receive element 122. Asnoted above, the WTRU 102 may have multi-mode capabilities. Thus, thetransceiver 120 may include multiple transceivers for enabling the WTRU102 to communicate via multiple RATs, such as UTRA and IEEE 802.11, forexample.

The processor 118 of the WTRU 102 may be coupled to, and may receiveuser input data from, the speaker/microphone 124, the keypad 126, and/orthe display/touchpad/indicators 128 (e.g., a liquid crystal display(LCD) display unit or organic light-emitting diode (OLED) display unit).The processor 118 may also output user data to the speaker/microphone124, the keypad 126, and/or the display/touchpad/indicators 128. Inaddition, the processor 118 may access information from, and store datain, any type of suitable memory, such as the non-removable memory 130and/or the removable memory 132. The non-removable memory 130 mayinclude random-access memory (RAM), read-only memory (ROM), a hard disk,or any other type of memory storage device. The removable memory 132 mayinclude a subscriber identity module (SIM) card, a memory stick, asecure digital (SD) memory card, and the like. In an embodiment, theprocessor 118 may access information from, and store data in, memorythat is not physically located on the WTRU 102, such as on a server or ahome computer (not shown).

The processor 118 may receive power from the power source 134, and maybe configured to distribute and/or control the power to the othercomponents in the WTRU 102. The power source 134 may be any suitabledevice for powering the WTRU 102. For example, the power source 134 mayinclude one or more dry cell batteries, solar cells, fuel cells, and thelike.

The processor 118 may also be coupled to the GPS chipset 136, which maybe configured to provide location information (e.g., longitude andlatitude) regarding the current location of the WTRU 102. In additionto, or in lieu of, the information from the GPS chipset 136, the WTRU102 may receive location information over the air interface 115/116/117from a base station (e.g., base stations 114 a, 114 b) and/or determineits location based on the timing of the signals being received from twoor more nearby base stations. It will be appreciated that the WTRU 102may acquire location information by way of any suitablelocation-determination method while remaining consistent with anembodiment.

The processor 118 may further be coupled to other peripherals 138, whichmay include one or more software and/or hardware modules that provideadditional features, functionality and/or wired or wirelessconnectivity. For example, the peripherals 138 may include varioussensors such as an accelerometer, biometrics (e.g., finger print)sensors, an e-compass, a satellite transceiver, a digital camera (forphotographs or video), a universal serial bus (USB) port or otherinterconnect interfaces, a vibration device, a television transceiver, ahands free headset, a Bluetooth® module, a frequency modulated (FM)radio unit, a digital music player, a media player, a video game playermodule, an Internet browser, and the like.

The WTRU 102 may be embodied in other apparatuses or devices, such as asensor, consumer electronics, a wearable device such as a smart watch orsmart clothing, a medical or eHealth device, a robot, industrialequipment, a drone, a vehicle such as a car, truck, train, or airplane.The WTRU 102 may connect to other components, modules, or systems ofsuch apparatuses or devices via one or more interconnect interfaces,such as an interconnect interface that may comprise one of theperipherals 138.

FIG. 53C is a system diagram of the RAN 103 and the core network 106according to an embodiment. As noted above, the RAN 103 may employ aUTRA radio technology to communicate with the WTRUs 102 a, 102 b, and102 c over the air interface 115. The RAN 103 may also be incommunication with the core network 106. As shown in FIG. 53C, the RAN103 may include Node-Bs 140 a, 140 b, 140 c, which may each include oneor more transceivers for communicating with the WTRUs 102 a, 102 b, 102c over the air interface 115. The Node-Bs 140 a, 140 b, 140 c may eachbe associated with a particular cell (not shown) within the RAN 103. TheRAN 103 may also include RNCs 142 a, 142 b. It will be appreciated thatthe RAN 103 may include any number of Node-Bs and RNCs while remainingconsistent with an embodiment.

As shown in FIG. 53C, the Node-Bs 140 a, 140 b may be in communicationwith the RNC 142 a. Additionally, the Node-B 140 c may be incommunication with the RNC 142 b. The Node-Bs 140 a, 140 b, 140 c maycommunicate with the respective RNCs 142 a, 142 b via an Iub interface.The RNCs 142 a, 142 b may be in communication with one another via anIur interface. Each of the RNCs 142 a, 142 b may be configured tocontrol the respective Node-Bs 140 a, 140 b, 140 c to which it isconnected. In addition, each of the RNCs 142 a, 142 b may be configuredto carry out or support other functionality, such as outer loop powercontrol, load control, admission control, packet scheduling, handovercontrol, macro-diversity, security functions, data encryption, and thelike.

The core network 106 shown in FIG. 53C may include a media gateway (MGW)144, a mobile switching center (MSC) 146, a serving GPRS support node(SGSN) 148, and/or a gateway GPRS support node (GGSN) 150. While each ofthe foregoing elements are depicted as part of the core network 106, itwill be appreciated that any one of these elements may be owned and/oroperated by an entity other than the core network operator.

The RNC 142 a in the RAN 103 may be connected to the MSC 146 in the corenetwork 106 via an IuCS interface. The MSC 146 may be connected to theMGW 144. The MSC 146 and the MGW 144 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices.

The RNC 142 a in the RAN 103 may also be connected to the SGSN 148 inthe core network 106 via an IuPS interface. The SGSN 148 may beconnected to the GGSN 150. The SGSN 148 and the GGSN 150 may provide theWTRUs 102 a, 102 b, 102 c with access to packet-switched networks, suchas the Internet 110, to facilitate communications between and the WTRUs102 a, 102 b, 102 c and IP-enabled devices.

As noted above, the core network 106 may also be connected to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 53D is a system diagram of the RAN 104 and the core network 107according to an embodiment. As noted above, the RAN 104 may employ anE-UTRA radio technology to communicate with the WTRUs 102 a, 102 b, and102 c over the air interface 116. The RAN 104 may also be incommunication with the core network 107.

The RAN 104 may include eNode-Bs 160 a, 160 b, 160 c, though it will beappreciated that the RAN 104 may include any number of eNode-Bs whileremaining consistent with an embodiment. The eNode-Bs 160 a, 160 b, 160c may each include one or more transceivers for communicating with theWTRUs 102 a, 102 b, 102 c over the air interface 116. In an embodiment,the eNode-Bs 160 a, 160 b, 160 c may implement MIMO technology. Thus,the eNode-B 160 a, for example, may use multiple antennas to transmitwireless signals to, and receive wireless signals from, the WTRU 102 a.

Each of the eNode-Bs 160 a, 160 b, and 160 c may be associated with aparticular cell (not shown) and may be configured to handle radioresource management decisions, handover decisions, scheduling of usersin the uplink and/or downlink, and the like. As shown in FIG. 53D, theeNode-Bs 160 a, 160 b, 160 c may communicate with one another over an X2interface.

The core network 107 shown in FIG. 53D may include a mobility managementgateway (MME) 162, a serving gateway 164, and a packet data network(PDN) gateway 166. While each of the foregoing elements are depicted aspart of the core network 107, it will be appreciated that any one ofthese elements may be owned and/or operated by an entity other than thecore network operator.

The MME 162 may be connected to each of the eNode-Bs 160 a, 160 b, and160 c in the RAN 104 via an S1 interface and may serve as a controlnode. For example, the MME 162 may be responsible for authenticatingusers of the WTRUs 102 a, 102 b, 102 c, bearer activation/deactivation,selecting a particular serving gateway during an initial attach of theWTRUs 102 a, 102 b, 102 c, and the like. The MME 162 may also provide acontrol plane function for switching between the RAN 104 and other RANs(not shown) that employ other radio technologies, such as GSM or WCDMA.

The serving gateway 164 may be connected to each of the eNode-Bs 160 a,160 b, and 160 c in the RAN 104 via the S1 interface. The servinggateway 164 may generally route and forward user data packets to/fromthe WTRUs 102 a, 102 b, 102 c. The serving gateway 164 may also performother functions, such as anchoring user planes during inter-eNode Bhandovers, triggering paging when downlink data is available for theWTRUs 102 a, 102 b, 102 c, managing and storing contexts of the WTRUs102 a, 102 b, 102 c, and the like.

The serving gateway 164 may also be connected to the PDN gateway 166,which may provide the WTRUs 102 a, 102 b, 102 c with access topacket-switched networks, such as the Internet 110, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and IP-enableddevices.

The core network 107 may facilitate communications with other networks.For example, the core network 107 may provide the WTRUs 102 a, 102 b,102 c with access to circuit-switched networks, such as the PSTN 108, tofacilitate communications between the WTRUs 102 a, 102 b, 102 c andtraditional land-line communications devices. For example, the corenetwork 107 may include, or may communicate with, an IP gateway (e.g.,an IP multimedia subsystem (IMS) server) that serves as an interfacebetween the core network 107 and the PSTN 108. In addition, the corenetwork 107 may provide the WTRUs 102 a, 102 b, 102 c with access to thenetworks 112, which may include other wired or wireless networks thatare owned and/or operated by other service providers.

FIG. 53E is a system diagram of the RAN 105 and the core network 109according to an embodiment. The RAN 105 may be an access service network(ASN) that employs IEEE 802.16 radio technology to communicate with theWTRUs 102 a, 102 b, and 102 c over the air interface 117. As will befurther discussed below, the communication links between the differentfunctional entities of the WTRUs 102 a, 102 b, 102 c, the RAN 105, andthe core network 109 may be defined as reference points.

As shown in FIG. 53E, the RAN 105 may include base stations 180 a, 180b, 180 c, and an ASN gateway 182, though it will be appreciated that theRAN 105 may include any number of base stations and ASN gateways whileremaining consistent with an embodiment. The base stations 180 a, 180 b,180 c may each be associated with a particular cell in the RAN 105 andmay include one or more transceivers for communicating with the WTRUs102 a, 102 b, 102 c over the air interface 117. In an embodiment, thebase stations 180 a, 180 b, 180 c may implement MIMO technology. Thus,the base station 180 a, for example, may use multiple antennas totransmit wireless signals to, and receive wireless signals from, theWTRU 102 a. The base stations 180 a, 180 b, 180 c may also providemobility management functions, such as handoff triggering, tunnelestablishment, radio resource management, traffic classification,quality of service (QoS) policy enforcement, and the like. The ASNgateway 182 may serve as a traffic aggregation point and may beresponsible for paging, caching of subscriber profiles, routing to thecore network 109, and the like.

The air interface 117 between the WTRUs 102 a, 102 b, 102 c and the RAN105 may be defined as an R1 reference point that implements the IEEE802.16 specification. In addition, each of the WTRUs 102 a, 102 b, and102 c may establish a logical interface (not shown) with the corenetwork 109. The logical interface between the WTRUs 102 a, 102 b, 102 cand the core network 109 may be defined as an R2 reference point, whichmay be used for authentication, authorization, IP host configurationmanagement, and/or mobility management.

The communication link between each of the base stations 180 a, 180 b,and 180 c may be defined as an R8 reference point that includesprotocols for facilitating WTRU handovers and the transfer of databetween base stations. The communication link between the base stations180 a, 180 b, 180 c and the ASN gateway 182 may be defined as an R6reference point. The R6 reference point may include protocols forfacilitating mobility management based on mobility events associatedwith each of the WTRUs 102 a, 102 b, 102 c.

As shown in FIG. 53E, the RAN 105 may be connected to the core network109. The communication link between the RAN 105 and the core network 109may defined as an R3 reference point that includes protocols forfacilitating data transfer and mobility management capabilities, forexample. The core network 109 may include a mobile IP home agent(MIP-HA) 184, an authentication, authorization, accounting (AAA) server186, and a gateway 188. While each of the foregoing elements aredepicted as part of the core network 109, it will be appreciated thatany one of these elements may be owned and/or operated by an entityother than the core network operator.

The MIP-HA may be responsible for IP address management, and may enablethe WTRUs 102 a, 102 b, and 102 c to roam between different ASNs and/ordifferent core networks. The MIP-HA 184 may provide the WTRUs 102 a, 102b, 102 c with access to packet-switched networks, such as the Internet110, to facilitate communications between the WTRUs 102 a, 102 b, 102 cand IP-enabled devices. The AAA server 186 may be responsible for userauthentication and for supporting user services. The gateway 188 mayfacilitate interworking with other networks. For example, the gateway188 may provide the WTRUs 102 a, 102 b, 102 c with access tocircuit-switched networks, such as the PSTN 108, to facilitatecommunications between the WTRUs 102 a, 102 b, 102 c and traditionalland-line communications devices. In addition, the gateway 188 mayprovide the WTRUs 102 a, 102 b, 102 c with access to the networks 112,which may include other wired or wireless networks that are owned and/oroperated by other service providers.

Although not shown in FIG. 53E, it will be appreciated that the RAN 105may be connected to other ASNs and the core network 109 may be connectedto other core networks. The communication link between the RAN 105 theother ASNs may be defined as an R4 reference point, which may includeprotocols for coordinating the mobility of the WTRUs 102 a, 102 b, 102 cbetween the RAN 105 and the other ASNs. The communication link betweenthe core network 109 and the other core networks may be defined as an R5reference, which may include protocols for facilitating interworkingbetween home core networks and visited core networks.

The core network entities described herein and illustrated in FIGS. 53A,53C, 53D, and 53E are identified by the names given to those entities incertain existing 3GPP specifications, but it is understood that in thefuture those entities and functionalities may be identified by othernames and certain entities or functions may be combined in futurespecifications published by 3GPP, including future 3GPP NRspecifications. Thus, the particular network entities andfunctionalities described and illustrated in FIGS. 53A, 53B, 53C, 53D,and 53E are provided by way of example only, and it is understood thatthe subject matter disclosed and claimed herein may be embodied orimplemented in any similar communication system, whether presentlydefined or defined in the future.

FIG. 53F is a block diagram of an exemplary computing system 90 in whichone or more apparatuses of the communications networks illustrated inFIGS. 53A, 53C, 53D and 53E may be embodied, such as certain nodes orfunctional entities in the RAN 103/104/105, Core Network 106/107/109,PSTN 108, Internet 110, or Other Networks 112. Computing system 90 maycomprise a computer or server and may be controlled primarily bycomputer readable instructions, which may be in the form of software,wherever, or by whatever means such software is stored or accessed. Suchcomputer readable instructions may be executed within a processor 91, tocause computing system 90 to do work. The processor 91 may be a generalpurpose processor, a special purpose processor, a conventionalprocessor, a digital signal processor (DSP), a plurality ofmicroprocessors, one or more microprocessors in association with a DSPcore, a controller, a microcontroller, Application Specific IntegratedCircuits (ASICs), Field Programmable Gate Array (FPGAs) circuits, anyother type of integrated circuit (IC), a state machine, and the like.The processor 91 may perform signal coding, data processing, powercontrol, input/output processing, and/or any other functionality thatenables the computing system 90 to operate in a communications network.Coprocessor 81 is an optional processor, distinct from main processor91, that may perform additional functions or assist processor 91.Processor 91 and/or coprocessor 81 may receive, generate, and processdata related to the methods and apparatuses disclosed herein.

In operation, processor 91 fetches, decodes, and executes instructions,and transfers information to and from other resources via the computingsystem's main data-transfer path, system bus 80. Such a system busconnects the components in computing system 90 and defines the mediumfor data exchange. System bus 80 typically includes data lines forsending data, address lines for sending addresses, and control lines forsending interrupts and for operating the system bus. An example of sucha system bus 80 is the PCI (Peripheral Component Interconnect) bus.

Memories coupled to system bus 80 include random access memory (RAM) 82and read only memory (ROM) 93. Such memories include circuitry thatallows information to be stored and retrieved. ROMs 93 generally containstored data that cannot easily be modified. Data stored in RAM 82 can beread or changed by processor 91 or other hardware devices. Access to RAM82 and/or ROM 93 may be controlled by memory controller 92. Memorycontroller 92 may provide an address translation function thattranslates virtual addresses into physical addresses as instructions areexecuted. Memory controller 92 may also provide a memory protectionfunction that isolates processes within the system and isolates systemprocesses from user processes. Thus, a program running in a first modecan access only memory mapped by its own process virtual address space;it cannot access memory within another process's virtual address spaceunless memory sharing between the processes has been set up.

In addition, computing system 90 may contain peripherals controller 83responsible for communicating instructions from processor 91 toperipherals, such as printer 94, keyboard 84, mouse 95, and disk drive85.

Display 86, which is controlled by display controller 96, is used todisplay visual output generated by computing system 90. Such visualoutput may include text, graphics, animated graphics, and video. Thevisual output may be provided in the form of a graphical user interface(GUI). Display 86 may be implemented with a CRT-based video display, anLCD-based flat-panel display, gas plasma-based flat-panel display, or atouch-panel. Display controller 96 includes electronic componentsrequired to generate a video signal that is sent to display 86.

Further, computing system 90 may contain communication circuitry, suchas for example a network adapter 97, that may be used to connectcomputing system 90 to an external communications network, such as theRAN 103/104/105, Core Network 106/107/109, PSTN 108, Internet 110, orOther Networks 112 of FIGS. 53A, 53B, 53C, 53D, and 53E, to enable thecomputing system 90 to communicate with other nodes or functionalentities of those networks. The communication circuitry, alone or incombination with the processor 91, may be used to perform thetransmitting and receiving steps of certain apparatuses, nodes, orfunctional entities described herein.

It is understood that any or all of the apparatuses, systems, methodsand processes described herein may be embodied in the form of computerexecutable instructions (e.g., program code) stored on acomputer-readable storage medium which instructions, when executed by aprocessor, such as processors 118 or 91, cause the processor to performand/or implement the systems, methods and processes described herein.Specifically, any of the steps, operations or functions described hereinmay be implemented in the form of such computer executable instructions,executing on the processor of an apparatus or computing systemconfigured for wireless and/or wired network communications. Computerreadable storage media include volatile and nonvolatile, removable andnon-removable media implemented in any non-transitory (e.g., tangible orphysical) method or technology for storage of information, but suchcomputer readable storage media do not includes signals. Computerreadable storage media include, but are not limited to, RAM, ROM,EEPROM, flash memory or other memory technology, CD-ROM, digitalversatile disks (DVD) or other optical disk storage, magnetic cassettes,magnetic tape, magnetic disk storage or other magnetic storage devices,or any other tangible or physical medium which can be used to store thedesired information and which can be accessed by a computing system.

The following is a list of acronyms relating to NR technologies that mayappear in the above description. Unless otherwise specified, theacronyms used herein refer to the corresponding term listed below.

-   -   AAS Active Antenna System    -   AoA Angle or Arrival    -   AoD Angle of Departure    -   AR Augmented Reality    -   AS Access Stratum    -   BF-RS Beam Form Reference Signal    -   CE Control Element    -   CoMP Coordinated Multipoint    -   CP Cyclic Prefix    -   CQI Channel Quality Indication    -   CRS Cell-specific Reference Signals    -   CSI Channel State Information    -   CSI-RS Channel State Information Reference Signals    -   DCI Downlink Control Information    -   DL DownLink    -   DM-RS Demodulation Reference Signals    -   eMBB enhanced Mobile Broadband    -   eNB evolved Node B    -   ePDCCH Enhanced Physical Downlink Control CHannel    -   FD Full-Dimension    -   FDD Frequency Division Duplex    -   FFS For Further Study    -   GUI Graphical User Interface    -   HARQ Hybrid Automatic Repeat Request    -   ID Identification    -   IMT International Mobile Telecommunications    -   KP Kronecker-Product    -   KPI Key Performance Indicators    -   LTE Long Term Evolution    -   MAC Medium Access Control    -   MCL Maximum Coupling Loss    -   MCS Modulation and Coding Scheme    -   MME Mobility Management Entity    -   MIMO Multiple-Input and Multiple-Output    -   NAS Non-Access Stratum    -   NB Narrow Beam    -   NDI New Data Indicator    -   NEO NEtwork Operation    -   NR-Node New Radio-Node    -   OCC Orthogonal Cover Codes    -   OFDM Orthogonal Frequency Division Multiplexing    -   PDCCH Physical Downlink Control Channel    -   PDSCH Physical Downlink Shared Channel    -   PMI Precoder Matrix Indication    -   PRS Positioning Reference Signals    -   PUSCH Physical Uplink Shared Channel    -   PUCCH Physical Uplink Control Channel    -   RAT Radio Access Technology    -   RB Resource Block    -   RE Resource Element    -   RI Rank Indication    -   RRC Radio Resource Control    -   RRH Remote Radio Head    -   RS Reference Signal    -   RSSI Received Signal Strength Indicator    -   RSRP Reference Signal Received Power    -   RSRQ Reference Signal Received Quality    -   RV Redundancy Version    -   SC-FDMA Single Carrier-Frequency Division Multiple Access    -   SI System Information    -   SIB System Information Block    -   SISO Single-Input and Single-Output    -   SRS Sounding Reference Signal    -   2D Two-Dimensional    -   3D Three-Dimensional    -   TDD Time Division Duplex    -   TPC Transmit Power Control    -   TRP Transmission and Reception Point    -   TTI Transmission Time Interval    -   UAV Unmanned Aerial Vehicle    -   UE User Equipment    -   UL UpLink    -   URLLC Ultra-Reliable and Low Latency Communications    -   VR Virtual Reality    -   WB Wide Beam    -   WRC Wireless Planning Coordination

What is claimed:
 1. An apparatus comprising a processor, a memory, andcommunication circuitry, the apparatus being connected to a network viaits communication circuitry, the apparatus further comprisingcomputer-executable instructions stored in the memory which, whenexecuted by the processor, cause the apparatus to perform operationscomprising: obtaining a first reference signal configuration and asecond reference signal configuration, the first and second referencesignal configurations being for a New Radio (NR) system; transmitting afirst reference signal on uplink in accordance with the first referencesignal configuration; and receiving a second reference signal ondownlink in accordance with the second reference signal configuration,wherein, at least one of the first and second reference signalconfigurations comprise: start time information indicating start time ofreference signal allocations in time domain; time allocation patterninformation; start frequency information indicating start frequency ofreference signal allocations in frequency domain; frequency allocationinformation indicating number of resource allocation for referencesignals in frequency domain; frequency allocation pattern informationindicating relation between subcarrier numbers and reference signalallocation numbers in frequency domain; and periodicity informationindicating periodicity of reference signal.
 2. The apparatus of claim 1,wherein the first reference signal configuration and the secondreference signal configurations pertain to Orthogonal Frequency DivisionMultiplexing (OFDM) symbols in time domain and to subcarriers orresource blocks in frequency domain.
 3. The apparatus of claim 1,wherein the periodicity information indicating periodicity of areference signal indicates that a reference signal is aperiodic.
 4. Theapparatus of claim 1, wherein the first reference signal configurationpertains to a Sounding Reference Signal (SRS).
 5. The apparatus of claim1, wherein the second reference signal configuration pertains to aChannel State Information Reference Signal (CSI-RS).
 6. The apparatus ofclaim 5, wherein the CSI-RS is used for mobility.
 7. The apparatus ofclaim 1, wherein the first reference signal configuration pertains to aDemodulation Reference Signal (DM-RS) on a Physical Uplink SharedChannel (PUSCH).
 8. The apparatus of 7, wherein the DMRS is located atthe beginning of an uplink time interval.
 9. The apparatus of claim 1,wherein the second reference signal configuration pertains to aDemodulation Reference Signal (DM-RS) on a Physical Downlink SharedChannel (PDSCH).
 10. The apparatus of 9, wherein the DMRS is located atthe beginning of an uplink time interval.
 11. A second apparatuscomprising a processor, a memory, and communication circuitry, theapparatus being connected to a network via its communication circuitry,the second apparatus further comprising computer-executable instructionsstored in the memory which, when executed by the processor, cause theapparatus to perform operations comprising: providing, to a firstapparatus, a first reference signal configuration and a second referencesignal configuration, the first and second reference signalconfigurations being for a New Radio (NR) system; receiving a firstreference signal on uplink in accordance with the reference signalconfiguration; and transmitting a second reference signal on downlink inaccordance with the second reference signal configuration, wherein, atleast one of the first and second reference signal configurationscomprise: start time information indicating start time of referencesignal allocations in time domain; time allocation pattern information;start frequency information indicating start frequency of referencesignal allocations in frequency domain; frequency allocation informationindicating number of resource allocation for reference signals infrequency domain; frequency allocation pattern information indicatingrelation between subcarrier numbers and reference signal allocationnumbers in frequency domain; and periodicity information indicatingperiodicity of reference signal.
 12. The second apparatus of claim 11,wherein the first reference signal configuration and the secondreference signal configurations pertain to Orthogonal Frequency DivisionMultiplexing (OFDM) symbols in time domain and to subcarriers orresource blocks in frequency domain.
 13. The second apparatus of claim11, wherein the periodicity information indicating periodicity of areference signal indicates that a reference signal is aperiodic.
 14. Thesecond apparatus of claim 11, wherein the first reference signalconfiguration pertains to a Sounding Reference Signal (SRS).
 15. Thesecond apparatus of claim 11, wherein the second reference signalconfiguration pertains to a Channel State Information Reference Signal(CSI-RS).
 16. The second apparatus of claim 15, wherein the CSI-RS isused for mobility.
 17. The second apparatus of claim 11, wherein thefirst reference signal configuration pertains to a DemodulationReference Signal (DM-RS) on a Physical Uplink Shared Channel (PUSCH).18. The second apparatus of claim 17, wherein the DMRS is located at thebeginning of an uplink time interval.
 19. The second apparatus of claim11, wherein the second reference signal configuration pertains to aDemodulation Reference Signal (DM-RS) on a Physical Downlink SharedChannel (PDSCH).
 20. The second apparatus of claim 19, wherein the DMRSis located at the beginning of an uplink time interval.